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Do healthy and unhealthy behaviours cluster in New Zealand?

Do healthy and unhealthy behaviours cluster in New Zealand? The role of health‐related behaviours as risk and protective factors in the causation and prevention of chronic disease is widely recognised. Yet few studies internationally, and to our knowledge none in New Zealand, have described the population distribution of clustering of health‐related behaviours within individuals. Such information about the distribution of ‘lifestyles’ within the population may be helpful in designing and evaluating health promotion policies and programs. The relatively few published studies 2–9 have varied in their selection of behaviours, their measure of clustering, and their analytical approach. Some have reported only the number of co‐occurring behaviours rather than specific behavioural patterns. Others have privileged one behaviour over others and defined clustering only in relation to this ‘central’ behaviour (most usually tobacco use). Most studies have focused exclusively on unhealthy behaviours to the neglect of healthy behaviours. The objective of the current study is to describe the clustering of both healthy and unhealthy behaviours in the New Zealand population today using a symmetric analytical approach. Since human behaviour does not occur in isolation from its social and cultural context, we examine how the clustering of behaviours (co‐occurrence of behaviours in the same individual greater than would be expected by chance) varies across socio‐demographic groups. Methods New Zealand Health Survey 2002/03 The New Zealand Health Survey (NZHS) was conducted from August 2002 to October 2003. The target population was the usually resident, non‐institutionalised civilian adult population (aged 15 years and over) living in permanent private dwellings. A stratified multistage cluster sample design was employed using an area‐based sampling frame. Details of the survey design and analysis, including calculation of integrated survey weights and standard errors for estimates, are reported elsewhere. For the present analysis, survey participants self‐reporting any present or past cardio‐vascular disease or cancer (any type) were excluded, since diagnosis of such diseases may lead to behaviour change (e.g. smoking cessation). This left 10,241 participants for analysis, comprising 3,416 Maori, 821 Pacific and 6,005 European/Others. Selection of behaviours Health‐related behaviours established as major risk or protective factors for chronic disease, in particular cardiovascular disease and cancer, include tobacco use, alcohol use, diet and physical activity. The healthy and unhealthy behaviours included in this study, together with their definitions and abbreviations, are summarised in Table 1 . For the purposes of this paper we define a ‘healthy lifestyle’ as one that incorporates all four healthy behaviours, and an ‘unhealthy lifestyle’ as one that features any three of the four unhealthy behaviours listed or all four of these behaviours. 1 Selected health‐related behaviours. Healthy behaviours Definitions Unhealthy Definitions behaviours Non‐smoking Never smoker, ex‐smoker, or non‐daily smoker Smoking One or more cigarettes per day Healthy drinking Abstainer or AUDIT score 7 or less Unhealthy drinking AUDIT score 8 or above (both sexes) Physically active 150 or more mins per week of activity equivalised to moderate intensity (∼3 METs) Inactive <150 mins per week of activity equivalised to moderate intensity Healthy diet 5 or more servings of fruit plus vegetables per day Unhealthy diet <5 servings of fruit plus vegetables per day Healthy lifestyle All 4 of the above Unhealthy lifestyle All 4, or any combination of 3 of the above The definition of ‘current smoking’ excludes non‐daily smokers because the self‐reporting of occasional or non‐daily use is less robust than that of daily use. The Alcohol Use Disorders Identification Test (AUDIT) is a widely used eight‐item scale identifying potentially hazardous drinking. A score of eight or more is generally accepted as indicative of a harmful quantity or pattern of drinking, although some investigators prefer a cut‐point of seven for females. The threshold for physical (in)activity of 150 minute per week of activity equivalised to moderate intensity is widely accepted as indicating sufficient physical activity for health. Five or more servings of fruit plus vegetables per day is used in the New Zealand Health Survey as a proxy measure for a healthy diet and correlates reasonably well with more compre‐hensive dietary assessments such as the Healthy Eating Index. Measurement of clustering Correlation between risk factors does not necessarily imply clustering. Rather, clustering exists when the observed distribution of the risk factors differs from that expected assuming the risk factors to be independent of each other. The expected joint prevalence of any set of risk factors is simply the product of the individual risk factor prevalences. For example, if the prevalence of smoking is 20% and the prevalence of drinking is 30%, then by the laws of probability the expected joint prevalence of [smoking + drinking] is 6%. If the observed prevalence exceeds the expected prevalence, clustering is said to occur. Analytical approach First, the observed prevalence of each singular behaviour and of all possible behavioural patterns (co‐occurrences of behaviours) is briefly described. Second, the association of each behavioural pattern with socio‐demographic variables is analysed by multiple logistic regression modelling. The model adjusts for age (in four categories: 15–24, 25–44, 45–64, 65+), sex, ethnicity (three categories as indicated above) and deprivation as a measure of socio‐economic position (five categories: quintiles of the NZDep2001 deprivation index, 1 being least deprived, 5 being most deprived). NZDep2001 is a Census‐based small area index of deprivation derived by principal component analysis of nine socio‐economic variables included in the 2001 Census. The reference group for the regression models is 25–44 years of age, male, European, deprivation quintile 5. While age is adjusted for in all reported odds ratios, the effect of age is not itself reported as this is biased by the exclusion of survey respondents with diagnosed cardiovascular disease or cancer. Finally, clustering (Observed/Expected prevalence ratio) is analysed for each behavioural pattern separately by socio‐demographic subgroup (i.e. a stratified analysis). Confidence intervals for the O/E or ‘clustering’ ratios were estimated by standard parametric methods for Poisson random variables. For all analyses, the prevalence or clustering of both healthy and unhealthy behaviours is reported. These are not mirror images of each other, because unhealthy behaviours are typically less prevalent than their healthy counterparts – so higher degrees of clustering are typically found for the former (since clustering is defined as a ratio measure). While this could be corrected by normalisation (re‐scaling), this has not been done since it is the actual degree of clustering that is important rather than the comparison of clustering of healthy compared with clustering of unhealthy behaviours. Prevalence rates have been age standardised to the World Health Organization (WHO) World Population by the direct method, and ethnicity standardised to the New Zealand 2001 Census population, where relevant. Ethnic standardisation is intended to enable comparison of degrees of clustering by deprivation level unconfounded by ethnicity. By contrast, comparison of clustering by ethnicity does not require standardisation for deprivation because deprivation is a mediator, not a confounder, of the ethnicity/outcome relationship. Results Descriptive epidemiology Healthy behaviours Table 2 shows the observed prevalence of single healthy behaviours in the New Zealand adult (15+) population, as well as the prevalence of a ‘healthy lifestyle’. Details of all healthy behavioural patterns are shown in Table 6 . 2 Healthy behaviour prevalence rates. Number a Prevalence (%) Non‐smoking Healthy drinking Physically active Healthy diet Healthy lifestyle b All (crude) 10,223 76.3 81.1 75.3 54.0 29.4 Age 15–24 1,517 73.2 67.1 76.1 44.9 20.5 25–44 4,664 72.4 80.5 74.5 51.9 26.2 45–64 2,918 80.0 87.9 78.6 60.0 36.8 65+ 1,124 90.2 94.7 66.8 66.7 41.9 Sex Male c 3,961 75.1 70.9 80.4 44.3 22.4 Female c 6,262 77.1 87.6 71.1 61.9 34.5 Ethnicity Maori c 3,406 50.4 71.2 77.0 49.5 18.6 Pacific c 819 67.3 80.8 67.2 38.4 15.9 Other c 5,998 79.8 80.5 75.9 54.7 30.6 SES Dep Q1 d 1,389 83.6 82.0 79.4 57.2 34.1 Dep Q2 d 1,300 81.4 79.6 77.0 59.3 33.2 Dep Q3 d 1,518 79.0 80.6 76.4 55.6 30.3 Dep Q4 d 1,950 72.4 78.7 74.1 49.1 23.8 Dep Q5 d 4,066 64.0 76.7 71.0 45.8 22.4 Notes: (a) Number of respondents included in analysis. (b) Healthy lifestyle = all four behaviours reported. (c) Age standardised. (d) Age and ethnicity standardised. 6 Clustering of healthy behaviours. S‐A‐P‐D S‐A‐P S‐A‐D S‐P‐D A‐P‐D All (crude) Observed 29.4 48.7 38.5 34.0 35.0 Expected 25.2 46.6 33.4 31.0 33.0 Ratio 1.17 a 1.05 a 1.15 a 1.10 a 1.06 a 15–24 years Observed 20.5 40.3 25.7 28.0 24.7 Expected 16.8 37.4 22.1 25.0 22.9 Ratio 1.22 a 1.08 a 1.17 a 1.12 a 1.08 25–44 years Observed 26.2 45.4 35.5 30.2 32.6 Expected 22.5 43.4 30.2 28.0 31.1 Ratio 1.16 a 1.05 a 1.17 a 1.08 a 1.05 a 45–64 years Observed 36.8 57.1 45.9 41.1 42.9 Expected 33.2 55.3 42.2 37.7 41.5 Ratio 1.11 a 1.03 1.09 a 1.09 a 1.03 65+ years Observed 41.9 57.9 59.0 43.6 45.4 Expected 38.1 57.1 57.0 40.2 42.2 Ratio 1.10 a 1.01 1.04 1.08 1.08 Male b Observed 22.4 45.8 27.4 29.0 26.7 Expected 19.0 42.8 23.6 26.7 25.3 Ratio 1.18 a 1.07 a 1.16 a 1.08 a 1.06 Female b Observed 34.5 50.0 46.6 37.9 40.9 Expected 29.7 48.0 41.8 33.9 38.6 Ratio 1.16 a 1.04 a 1.11 a 1.12 a 1.06 a Maori b Observed 18.6 30.6 22.6 23.2 30.2 Expected 13.7 27.6 17.8 19.2 27.1 Ratio 1.36 a 1.11 a 1.27 a 1.21 a 1.11 a Pacific b Observed 15.9 42.1 22.9 17.9 22.0 Expected 14.0 36.5 20.9 17.4 20.9 Ratio 1.13 1.15 a 1.10 1.03 1.06 Other b Observed 30.6 50.4 39.9 35.8 35.2 Expected 26.7 48.8 35.1 33.1 33.4 Ratio 1.15 a 1.03 a 1.14 a 1.08 a 1.05 a Quintile 1 c Observed 34.1 55.1 42.4 39.1 38.5 Expected 29.4 52.2 37.2 36.5 35.9 Ratio 1.15 a 1.03 1.11 a 1.07 1.06 Quintile 2 c Observed 33.2 51.0 42.6 38.1 38.7 Expected 28.5 49.9 37.3 35.8 35.5 Ratio 1.15 a 1.04 1.13 a 1.06 1.09 Quintile 3 c Observed 30.3 48.4 39.9 35.4 35.6 Expected 26.5 47.9 34.7 33.1 33.8 Ratio 1.14 a 1.01 1.14 a 1.07 1.05 Quintile 4 c Observed 23.8 44.3 32.3 28.9 29.0 Expected 20.8 42.3 28.0 26.5 28.6 Ratio 1.14 a 1.04 1.15 a 1.09 a 1.01 Quintile 5 c Observed 22.4 40.5 29.3 27.4 28.0 Expected 17.1 35.5 23.9 22.7 26.0 Ratio 1.31 a 1.14 a 1.22 a 1.21 a 1.08 a Notes: (a) p value <0.05. (b) Age standardised. (c) Age and ethnicity standardised. S=non smoking; A=healthy drinking; P=sufficient physical activity; D=healthy diet. Overall, 76% of New Zealand adults are non‐smokers, 81% have a healthy drinking pattern, 75% are sufficiently physically active for health, and 54% consume a healthy diet (as indexed by sufficient fruit and vegetable intake). However, this overall assessment disguises substantial variations between population subgroups, with older people more likely to exhibit healthy behaviours (except for physical activity) than youth; females than males (again except for physical activity); European/Others than Maori or Pacific people; and deprivation quintile 1 (the least deprived) than quintile 5 (the most deprived). Almost 30% of adults report a healthy lifestyle (as defined). However, this again varies with age, from 20% in youth to more than 40% in older people. It also varies with sex, being higher in females (35%) than males (22%) after standardising for age. Maori and Pacific ethnic groups have lower prevalence of the healthy lifestyle (19% and 16% respectively) than European/Others (31%), adjusting for age but not deprivation. A socio‐economic gradient was found, with the prevalence of the healthy lifestyle varying from 34% in deprivation quintile 1 (least deprived) to 22% in quintile 5 (most deprived), adjusting for age and ethnicity. Unhealthy behaviours Table 3 shows the observed prevalence of single unhealthy behaviours in the New Zealand adult (15+) population, as well as the prevalence of unhealthy lifestyle. Detailed prevalences of all unhealthy behavioural patterns are shown in Table 7 . 3 Unhealthy behaviour prevalence rates. Number a Prevalence (%) Smoking Unhealthy drinking Insufficiently active Unhealthy diet Unhealthy lifestyle – all 4 behaviours Unhealthy lifestyle – any 3 of 4 behaviours All (crude) 10,223 23.7 18.9 24.7 46.0 1.4 13.6 Age 15–24 1,517 26.8 32.9 23.9 55.1 3.3 22.9 25–44 4,664 27.6 19.5 25.5 48.1 1.4 14.8 45–64 2,918 20.0 12.1 21.4 40.0 0.5 7.9 65+ 1,124 9.8 5.3 33.2 33.3 Sex Male b 3,961 24.9 29.1 19.6 55.7 1.8 17.2 Female b 6,262 22.9 12.4 28.9 38.1 1.4 11.8 Ethnicity Maori b 3,406 49.6 28.8 23.0 50.5 2.4 26.3 Pacific b 819 32.7 19.2 32.8 61.6 4.0 28.1 Other b 5,998 20.2 19.5 24.1 45.3 1.4 12.1 SES DepQ1 c 1,389 16.4 18.0 20.6 42.8 d d DepQ2 c 1,300 18.6 20.4 23.0 40.7 1.0 11.5 DepQ3 c 1,518 21.0 19.4 23.6 44.4 0.7 10.0 DepQ4 c 1,950 27.6 21.3 25.9 50.9 1.3 15.1 DepQ5 c 4,066 36.0 23.3 29.0 54.2 3.3 25.9 Notes: (a) Number of respondents included in analysis. (b) Age standardised. (c) Age and ethnicity standardised. (d) Count suppressed (<10). 7 Clustering of unhealthy behaviours. S‐A‐P‐D S‐A‐P S‐A‐D S‐P‐D A‐P‐D All (crude) Observed 1.4 2.0 5.0 4.0 2.6 Expected 0.5 1.1 2.1 2.7 2.1 Ratio 2.75 a 1.81 a 2.43 a 1.49 a 1.21 a 15–24 years Observed 3.3 4.2 8.8 5.5 4.4 Expected 1.2 2.1 4.9 3.5 4.3 Ratio 2.84 a 1.99 a 1.81 a 1.56 a 1.02 25–44 years Observed 1.4 2.0 5.5 4.4 2.9 Expected 0.7 1.4 2.6 3.4 2.4 Ratio 2.12 a 1.46 a 2.12 a 1.30 a 1.21 a 45–64 years Observed 0.5 0.9 2.9 2.9 1.2 Expected 0.2 0.5 1.0 1.7 1.0 Ratio 2.41 1.74 a 3.00 a 1.69 a 1.16 65+ years Observed – – – 1.7 1.3 Expected – – – 1.1 0.6 Ratio – – – 1.57 2.22 a Male b Observed 1.8 2.4 7.3 3.7 3.8 Expected 0.8 1.4 4.0 2.7 3.2 Ratio 2.28 a 1.69 a 1.81 a 1.36 a 1.20 a Female b Observed 1.4 2.0 3.5 4.5 1.8 Expected 0.3 0.8 1.1 2.5 1.4 Ratio 4.48 a 2.44 a 3.24 a 1.78 a 1.32 a Maori b Observed 2.4 3.8 10.9 8.0 3.6 Expected 1.7 3.3 7.2 5.8 3.3 Ratio 1.45 a 1.16 1.51 a 1.39 a 1.08 Pacific b Observed 4.0 5.2 8.4 8.7 5.4 Expected 1.3 2.1 3.9 6.9 3.9 Ratio 3.15 a 2.53 a 2.17 a 1.32 a 1.39 a Other b Observed 1.4 1.8 4.5 3.3 2.5 Expected 0.4 0.9 1.8 2.2 2.1 Ratio 3.26 a 1.90 a 2.52 a 1.50 a 1.17 a Quintile 1 c Observed – 1.8 4.8 2.8 2.9 Expected – 0.7 1.5 1.6 1.8 Ratio – 2.57 a 3.20 a 1.75 a 1.64 a Quintile 2 c Observed 1.2 1.7 4.2 2.8 2.8 Expected 0.4 0.9 1.7 1.9 2.0 Ratio 3.10 a 1.83 a 2.46 a 1.41 a 1.41 a Quintile 3 c Observed 0.7 1.0 5.2 2.4 1.4 Expected 0.5 1.0 1.9 2.2 2.1 Ratio 1.40 1.04 2.76 a 1.09 0.70 Quintile 4 c Observed 1.3 2.3 5.3 4.5 3.0 Expected 0.8 1.5 3.0 3.6 2.8 Ratio 1.68 1.51 a 1.80 a 1.24 1.03 Quintile 5 c Observed 3.3 4.3 8.5 8.3 4.8 Expected 1.2 2.4 4.4 5.0 3.6 Ratio 2.75 a 1.77 a 1.94 a 1.66 a 1.33 a Notes: (a) p value <0.05. (b) Age standardised. (c) Age and ethnicity standardised. S=smoking; A=unhealthy drinking; P=insufficient physical activity; D=unhealthy diet. Rates were not calculated when counts less than 10. Overall, 24% of New Zealanders currently smoke cigarettes, 19% exhibit a hazardous drinking pattern, 25% are insufficiently physically active for health, and 46% consume an unhealthy diet (as indexed by inadequate intake of fruit and vegetables). As with the corresponding healthy behaviours, differences are seen with age, sex, ethnicity and deprivation as shown in Table 3 . Turning to the unhealthy lifestyle construct, approximately 15% of the population may be characterised as having an unhealthy lifestyle (defined as any three or all four unhealthy behaviours), although only 1.5% of the population acknowledge all four unhealthy behaviours. The prevalence of an unhealthy lifestyle varies with age (26% in youth, 8% in middle‐aged adults), sex (19% in males, 13% in females, age adjusted), ethnicity (29% in Maori, 32% in Pacific people, 13.5% in Others, adjusting for age) and deprivation quintile (from 13% in quintile 2 to 29% in quintile 5, adjusting for age and ethnicity). Co‐occurrence: regression analysis Healthy behaviours Table 4 summarises the model output for all healthy behaviour patterns (i.e. co‐occurrence, not clustering); two‐behaviour patterns are not shown but are available from the first author on request. 4 Odds ratios and 95% CIs for healthy behaviour patterns. S‐A‐P‐D A‐P‐D S‐P‐D S‐A‐D S‐A‐P Female 1.83 1.91 1.47 2.39 1.18 (1.60–2.09) (1.69–2.16) (1.30–1.67) (2.11–2.71) (1.05–1.34) Maori 0.57 0.89 0.62 0.47 0.47 (0.44–0.73) (0.72–1.09) (0.48–0.79) (0.37–0.59) (0.39–0.57) Pacific 0.52 0.65 0.49 0.50 0.86 (0.39–0.71) (0.48–0.88) (0.36–0.67) (0.38–0.67) (0.64–1.15) Q1 1.83 1.71 1.76 1.81 1.74 (1.41–2.38) (1.34–2.18) (1.35–2.29) (1.41–2.33) (1.39–2.17) Q2 1.84 1.75 1.80 1.84 1.50 (1.42–2.38) (1.37–2.24) (1.38–2.35) (1.42–2.38) (1.20–1.88) Q3 1.55 1.47 1.48 1.63 1.32 (1.21–1.99) (1.16–1.86) (1.16–1.90) (1.29–2.07) (1.05–1.67) Q4 1.10 1.10 1.09 1.17 1.11 (0.85–1.41) (0.88–1.38) (0.86–1.38) (0.91–1.50) (0.89–1.37) Notes: Reference group is male, European/Other, Deprivation Quintile 5. S=non‐smoking; A=healthy drinking; P= sufficient physical activity; D=healthy diet. Two‐behaviour patterns not shown (available from first author on request). Females are almost twice as likely as males to enjoy a healthy lifestyle (odds ratio 1.8). Females also have significantly higher prevalences of all three and two‐behaviour patterns (co‐occurrences) except for the [non‐smoking + sufficient activity] pattern that occurs 20% less often than in males, a difference that is also statistically significant at the 95% level. Maori are less likely than European/Others to exhibit healthy lifestyles and all three‐ and two‐behaviour patterns except for [physically active + healthy diet], for which there is no difference. The results for Pacific people are essentially the same, although not all differences are statistically significant – perhaps due to the relatively smaller numbers in the sample. A clear socio‐economic gradient in the prevalence of healthy lifestyles and all three‐ and two‐behaviour patterns is evident from the deprivation analysis, adjusting for age, sex and ethnicity. Unhealthy behaviours Table 5 summarises the model output for all unhealthy behaviour patterns (i.e. co‐occurrence, not clustering); two‐behaviour patterns are not shown but are available from the first author on request. 5 Odds ratios and 95% CIs for unhealthy behaviour patterns. S‐A‐P‐D A‐P‐D S‐P‐D S‐A‐D S‐A‐P Female 0.67 0.42 1.18 0.42 0.71 (0.42–1.08) (0.29–0.62) (0.86–1.62) (0.32–0.55) (0.48–1.05) Maori 1.48 1.27 1.80 2.44 1.68 (0.67–3.29) (0.69–2.33) (1.17–2.78) (1.68–3.55) (0.84–3.36) Pacific 1.91 1.56 1.53 1.65 2.10 (0.83–4.38) (0.83–2.94) (0.90–2.61) (0.87–3.12) (0.97–4.54) Q1 0.55 0.60 0.31 0.50 0.47 (0.21–1.42) (0.31–1.20) (0.16–0.60) (0.27–0.92) (0.18–1.23) Q2 0.39 0.70 0.31 0.54 0.48 (0.15–1.03) (0.36–1.36) (0.18–0.54) (0.31–0.96) (0.21–1.08) Q3 0.26 0.34 0.31 0.67 0.30 (0.09–0.76) (0.15–0.75) (0.19–0.52) (0.39–1.17) (0.12–0.74) Q4 0.46 0.71 0.56 0.68 0.70 (0.21–1.02) (0.40–1.26) (0.36–0.86) (0.43–1.09) (0.34–1.45) Notes: Reference group is male, European/Other, Deprivation Quintile 5. S=current daily smoking; A=unhealthy drinking; P=insufficient activity for health; D=unhealthy diet (inadequate fruit and vegetable intake). Two behaviour patterns not shown (available from first author on request). Females are less likely than males to show an unhealthy lifestyle, although not all differences are statistically significant. Females are significantly less likely than males to show all of the two‐behaviour patterns except [smoking + insufficient physical activity] (which they are significantly more likely to exhibit) and [unhealthy diet + insufficient physical activity] for which the gender difference is not statistically significant. Confidence intervals for Maori and Pacific ethnic groups are wide, making it difficult to demonstrate significant differences. However, the results are suggestive of higher prevalences for all unhealthy behaviour patterns. Unlike the situation for healthy behaviours, there is less of a clear gradient in unhealthy behaviour patterns across the deprivation quintiles after adjustment for age, sex and ethnicity. There is a tendency, however, for quintiles 1–4, and especially quintiles 1–3, to have lower (sometimes significantly lower) prevalences of all unhealthy behaviour patterns than quintile 5. Clustering: stratified analysis Healthy behaviours Table 6 shows the observed and expected prevalences for all healthy behaviour patterns (except for the two‐behaviour patterns – available from the first author on request), and the corresponding O/E ratios (‘clustering ratios’). Confidence intervals for the ratios are not shown for clarity (available from the first author on request), but those with p values <0.05 are identified. In the total New Zealand population, a small but statistically significant degree of clustering is seen for most healthy behaviour patterns (i.e. the prevalence of co‐occurrence is typically greater than would be expected if the component behaviours were independent). The healthy lifestyle pattern shows the highest degree of clustering (a ratio of 1.17, 95% confidence interval 1.13–1.21). That is, the proportion of individuals exhibiting all four behaviours was 29%, which is 17% higher than the 25% that would have been expected had the four component healthy behaviours been independently distributed across the population. All three‐behaviour patterns show clustering ratios ranging from 1.05 to 1.15. Less clustering is seen for the two‐behaviour patterns, with [non‐smoking + sufficient activity] and [healthy drinking + sufficient activity] showing no clustering at all. Clustering varies with age, with younger age groups showing more clustering than older age groups. Indeed, older people (65+) show no clustering at all except for overall healthy lifestyle (clustering ratio 1.10, 95% CI 1.01–1.20). Few significant gender differences were found after standardising for age. Maori demonstrate higher degrees of clustering of healthy behaviours than do European/Others. Healthy lifestyle has an O/E ratio of 1.36 (CI 1.26–1.46) in Maori compared with only 1.15 (CI 1.09–1.20) in European/Others. Other major differences include [non‐smoking + healthy drinking + healthy diet]: 1.27 versus 1.14; [non‐smoking + sufficiently active + healthy diet]: 1.21 versus 1.08; [non‐smoking + healthy drinking]: 1.10 versus 1.05; and [non‐smoking + healthy diet]: 1.11 versus 1.05 respectively. Little if any difference in the nature or extent of clustering of healthy behaviours is seen across deprivation quintiles 1–4, but quintile 5 displays higher degrees of clustering for some patterns, including the healthy lifestyle pattern itself (1.25 versus 1.11 for quintile 1). Compared with quintile 1, quintile 5 also exhibits substantial clustering in regard to [non‐smoking + sufficiently active + healthy diet]: 1.17 versus 1.05; and [non‐smoking + healthy drinking]: 1.10 versus none (1.00). Unhealthy behaviours Table 7 shows the observed and expected prevalences for all unhealthy behaviour patterns (other than the two‐behaviour patterns, which are available from the first author on request), and the corresponding O/E (‘clustering’) ratios. Confidence intervals for the ratios are not shown for clarity (available from the first author on request), but those with p values <0.05 are identified. For the total New Zealand population, moderate or high degrees of clustering are seen for some patterns (especially the four‐ and three‐behaviour patterns), with slight or no clustering for most of the two‐behaviour patterns. The ‘four behaviour unhealthy lifestyle’ pattern is highly clustered (O/E ratio 2.75, CI 2.29–3.21). Almost as much clustering is found for one of the three‐behaviour unhealthy lifestyle patterns, namely [smoking + unhealthy drinking + unhealthy diet] (clustering ratio 2.43, CI 2.19–2.66). The remaining three‐behaviour unhealthy lifestyle patterns show moderate to slight clustering. One two‐behaviour pattern – [smoking + unhealthy drinking] – also shows a high degree of clustering (ratio 1.79, CI 1.65–1.92). Males and females show the same overall pattern, but the degree of clustering of unhealthy behaviours (when present) is always greater for females than males. For example, the four‐behaviour unhealthy lifestyle pattern has a clustering ratio of 4.48 in females compared with 2.28 in males, after adjusting for age. Other major gender differences are seen with the three‐behaviour pattern [smoking + unhealthy drinking + unhealthy diet]: 3.24 versus 1.81; and the two‐behaviour pattern [smoking + unhealthy drinking]: 2.11 versus 1.57 respectively. There are few differences in the extent or nature of clustering with age, at least to 64 years. Not all behaviour patterns could be assessed in the 65+ age group because of small numbers in some cells. However, it does appear that clustering of the two‐behaviour pattern [smoking + unhealthy drinking] does increase with age, from a clustering ratio of 1.58 in youth to 1.93 in older people. Pacific people show much the same pattern and extent of clustering as European/Others. However, Maori consistently show less clustering of unhealthy behaviours than the other ethnic groups (despite showing more clustering of healthy behaviours). For example, the four‐behaviour unhealthy lifestyle is clustered to an O/E ratio of only 1.45 in Maori versus 3.15 in Pacific people and 3.26 in European/Others. As another example, the [smoking + unhealthy drinking] pattern has a clustering ratio of only 1.26 in Maori (although this is still statistically significant) compared with 1.85 in both of the other ethnic groups. There is very little if any evidence for a gradient in clustering across deprivation quintiles. If anything, for several unhealthy behaviour patterns the degree of clustering tends to be slightly greater in quintiles 1–2 than in the other quintiles. For example, the important two‐behaviour pattern [smoking + unhealthy drinking] has a clustering ratio of 2.26 in Q1, 1.79 in Q2, 1.79 in Q3, 1.67 in Q4 and 1.59 in Q5. Discussion Concept of clustering The concept of clustering is not clearly defined in the literature, and different authors have theorised and operationalised this construct in different ways. An important contribution of this study has been to clarify the definition of clustering as co‐occurrence greater than that expected by chance. Clustering thus implies that the distribution of the risk factors concerned is not independent of each other, but instead reflects a common, more distal, determinant. Thus finding clustering – or not – has both policy and research implications, some of which are elaborated below. Healthy behaviours Our study finds that, in 2002/03, approximately 29% of adult New Zealanders enjoyed a healthy lifestyle characterised by non‐use of tobacco, safe or non‐use of alcohol, sufficient physical activity for health, and a healthy diet as indexed by adequate fruit and vegetable consumption. This is very similar to rates reported for Australia, the United Kingdom and Finland, despite differences between studies in the definitions and thresholds for these health‐related behaviours. It is higher than rates reported for the United States, with better physical activity and fruit and vegetable consumption rates being reported for New Zealand, but again differing definitions make the comparison inexact. While in line with at least some other developed countries, and perhaps higher than many public health workers might have predicted, our results imply that more than two‐thirds of adults are still not meeting even modest thresholds for healthy living. Or more positively, this finding reveals the great scope still available for health gain via improvements in lifestyle. Of even more interest, we found that healthy behaviours show little clustering within individuals. For example, independent distribution of all four health‐related behaviours selected for study would have yielded a joint prevalence of 25% rather than the 29% actually observed – indicating only 17% clustering (i.e. a clustering or observed/expected ratio of 1.17). Even less clustering was found for all the three‐behaviour and two‐behaviour patterns. Such low levels of clustering of healthy behaviours has also been found in other studies. This finding has implications, for example, for research into the health benefits of fruit and vegetable consumption. Such research has often been criticised on the grounds that fruit and vegetable consumption is merely a marker of a healthy lifestyle, so any association between such consumption and health outcomes may be subject to residual confounding by other dimensions of a healthy lifestyle (e.g. non‐smoking, healthy drinking, sufficient physical activity) rather than reflecting a true dietary impact. Our analysis, finding little or no clustering of healthy behaviours within individuals, refutes this hypothesis. Unhealthy behaviours Our study found that, in 2002/03, less than 1.5% of adult New Zealanders exhibited all four of the selected unhealthy behaviours (i.e. daily tobacco use, potentially hazardous alcohol consumption in terms of volume or drinking pattern, insufficient physical activity for health, and inadequate intake of fruit and vegetables as an indicator of wider dietary pattern). Again, this is similar to the rate found in some other developed countries, especially if allowance is made for differences in variable definition, behavioural thresholds, and study design. Using a wider definition of unhealthy lifestyle to include any three as well as all four unhealthy behaviours, then 15% of the adult population would be so categorised. Youth (23%), males (17%), people living in the most deprived 20% of small areas (26%), Maori (26%) and Pacific people (28%) exhibited higher‐than‐average prevalences of these behaviour patterns. For the latter three socio‐demographic groups the proportion with an unhealthy lifestyle was higher than the corresponding proportion with a healthy lifestyle. Turning to clustering, even the low prevalence of the ‘four‐behaviour unhealthy lifestyle’ observed (approximately 1.5%) is almost three times higher than the 0.5% prevalence expected given independent risk factor distributions. The three‐behaviour unhealthy lifestyles show lesser but still substantial degrees of clustering. The two‐behaviour patterns show progressively less clustering than the three‐behaviour patterns with the exception of the co‐occurrence of tobacco and potentially hazardous alcohol consumption, which co‐occurs almost twice as often as expected, a finding that has been reported previously in other countries. Interestingly, insufficient physical activity and unhealthy diet (insufficient fruit and vegetable intake) were not found to cluster to more than a very minor degree – contrary to what might have been hypothesised if physical inactivity contributed substantively to the obesity epidemic. Unlike the situation with healthy behaviours, Maori exhibited less clustering than other ethnic groups for most unhealthy behaviour patterns. While Maori experience higher prevalences of most of the individual risk factors, recent research suggests that unhealthy behaviours – including tobacco use – make a smaller contribution to the ethnic disparity in health than previously estimated. Our study suggests that clustering of unhealthy behaviours makes no contribution to the Maori/non‐Maori health disparity at all. Analogously, it is generally the case that more disadvantaged or lower status groups have higher risk factor prevalences than their more powerful and privileged counterparts, yet differences in the distribution of singular unhealthy behaviours explain relatively little of the socio‐economic gradient in ischaemic heart disease. It has been hypothesised that greater clustering of risk factors might explain more of the gradient, yet our results do not support the notion of a social gradient in clustering of unhealthy behaviours. Health system Our findings on clustering (or lack thereof) of both healthy and unhealthy behaviours are new (for New Zealand) and have implications for health promotion policy and practice both in New Zealand and abroad. Conventional population‐based health promotion programs have tended to focus on single issues, while individual‐based (clinical) services tend towards the case management approach of dealing with multiple factors simultaneously (e.g. absolute cardiovascular risk). The current work supports both these approaches. The relative lack of clustering of healthy behaviours shows that single issue initiatives (e.g. separately promoting fruit and vegetable consumption and walking) are generally appropriate for most universal strategies (because the lack of substantial clustering means that little spin‐off can be expected from one dimension of health to another). Conversely, the clustering of multiple unhealthy behaviours in a relatively small number of people justifies a case management approach to ‘high‐risk’ strategies. Targeted chronic care management and integrated care initiatives emanating from the personal health sector will thus meet – and reinforce – universal public health initiatives coming the other way. Yet three caveats should be borne in mind in using our results for planning either clinical or population‐based preventive interventions. First, exclusion of survey participants with a history of cardiovascular disease or cancer may have introduced bias, especially for older males. It is unlikely, however, that this could have been sufficient to affect our conclusions regarding the extent of clustering. Second, different results may be obtained if different behaviours are selected for study, if those behaviours are defined and operationalised differently, and if different thresholds for categorising the behaviours are chosen. Indeed, our dichotomisation of behaviours represents a major simplification, and a more nuanced approach that recognised varying degrees of behavioural expression (e.g. light, moderate and heavy smoking) might be preferable. Yet contrasts between groups and trends over time in the extent of clustering may still be validly estimated, provided the method is consistently applied. Some analyses have included overweight/obesity (defined via body mass index or waist circumference) in behaviour clustering studies. Given that obesity is not a behaviour per se, we prefer to use measures of physical activity and nutrition directly. Finally, a policy focus on behavioural clustering risks being counterproductive if it decontextualises human behaviour and neglects the social forces that shape behavioural repertoires and their expression in different settings. The lifestyle construct as applied in this study does not imply free and unconstrained behavioural choices by individuals or families. Provided this is understood, we conclude that measurement and monitoring of behavioural clustering can be a useful tool for health promotion, helping to identify intervention points (‘over‐represented’ behavioural patterns within socio‐demographic and geographic subgroups) and evaluate outcomes relating to such intervention points. We have shown that 29% of adults in New Zealand live a relatively healthy lifestyle, being non‐smokers, eating 5+ vegetables and fruit a day, being moderately active, and indulging in non‐harmful use (or non‐use) of alcohol. Conversely, 15% live a relatively unhealthy lifestyle, with any three or all four unhealthy behaviours. There is clearly still much scope for health gain via health promotion. Clustering tendencies were not strong, especially for healthy behaviours, and did not display any social gradient or ethnic disparity. Hence clustering of unhealthy behaviours cannot explain any of the well‐established ethnic or socio‐economic disparities in the burden of chronic disease. Moreover, while a clinical case management approach seems appropriate for the 15% of the population with unhealthy lifestyles, promotion of healthy lifestyles via population‐based programs will need to focus on single issues and little spin‐off from one issue to another can be expected. Acknowledgements We thank the 13,000 New Zealanders who freely gave of their time to participate in the 2002/03 New Zealand Health Survey. This report is published with the approval of the Deputy Director‐General (Public Health). However, opinions expressed are those of the authors and do not necessarily reflect the views of the Ministry of Health or the Counties Manukau District Health Board. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian and New Zealand Journal of Public Health Wiley

Do healthy and unhealthy behaviours cluster in New Zealand?

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References (19)

Publisher
Wiley
Copyright
Copyright © 2007 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1326-0200
eISSN
1753-6405
DOI
10.1111/j.1753-6405.2007.00034.x
Publisher site
See Article on Publisher Site

Abstract

The role of health‐related behaviours as risk and protective factors in the causation and prevention of chronic disease is widely recognised. Yet few studies internationally, and to our knowledge none in New Zealand, have described the population distribution of clustering of health‐related behaviours within individuals. Such information about the distribution of ‘lifestyles’ within the population may be helpful in designing and evaluating health promotion policies and programs. The relatively few published studies 2–9 have varied in their selection of behaviours, their measure of clustering, and their analytical approach. Some have reported only the number of co‐occurring behaviours rather than specific behavioural patterns. Others have privileged one behaviour over others and defined clustering only in relation to this ‘central’ behaviour (most usually tobacco use). Most studies have focused exclusively on unhealthy behaviours to the neglect of healthy behaviours. The objective of the current study is to describe the clustering of both healthy and unhealthy behaviours in the New Zealand population today using a symmetric analytical approach. Since human behaviour does not occur in isolation from its social and cultural context, we examine how the clustering of behaviours (co‐occurrence of behaviours in the same individual greater than would be expected by chance) varies across socio‐demographic groups. Methods New Zealand Health Survey 2002/03 The New Zealand Health Survey (NZHS) was conducted from August 2002 to October 2003. The target population was the usually resident, non‐institutionalised civilian adult population (aged 15 years and over) living in permanent private dwellings. A stratified multistage cluster sample design was employed using an area‐based sampling frame. Details of the survey design and analysis, including calculation of integrated survey weights and standard errors for estimates, are reported elsewhere. For the present analysis, survey participants self‐reporting any present or past cardio‐vascular disease or cancer (any type) were excluded, since diagnosis of such diseases may lead to behaviour change (e.g. smoking cessation). This left 10,241 participants for analysis, comprising 3,416 Maori, 821 Pacific and 6,005 European/Others. Selection of behaviours Health‐related behaviours established as major risk or protective factors for chronic disease, in particular cardiovascular disease and cancer, include tobacco use, alcohol use, diet and physical activity. The healthy and unhealthy behaviours included in this study, together with their definitions and abbreviations, are summarised in Table 1 . For the purposes of this paper we define a ‘healthy lifestyle’ as one that incorporates all four healthy behaviours, and an ‘unhealthy lifestyle’ as one that features any three of the four unhealthy behaviours listed or all four of these behaviours. 1 Selected health‐related behaviours. Healthy behaviours Definitions Unhealthy Definitions behaviours Non‐smoking Never smoker, ex‐smoker, or non‐daily smoker Smoking One or more cigarettes per day Healthy drinking Abstainer or AUDIT score 7 or less Unhealthy drinking AUDIT score 8 or above (both sexes) Physically active 150 or more mins per week of activity equivalised to moderate intensity (∼3 METs) Inactive <150 mins per week of activity equivalised to moderate intensity Healthy diet 5 or more servings of fruit plus vegetables per day Unhealthy diet <5 servings of fruit plus vegetables per day Healthy lifestyle All 4 of the above Unhealthy lifestyle All 4, or any combination of 3 of the above The definition of ‘current smoking’ excludes non‐daily smokers because the self‐reporting of occasional or non‐daily use is less robust than that of daily use. The Alcohol Use Disorders Identification Test (AUDIT) is a widely used eight‐item scale identifying potentially hazardous drinking. A score of eight or more is generally accepted as indicative of a harmful quantity or pattern of drinking, although some investigators prefer a cut‐point of seven for females. The threshold for physical (in)activity of 150 minute per week of activity equivalised to moderate intensity is widely accepted as indicating sufficient physical activity for health. Five or more servings of fruit plus vegetables per day is used in the New Zealand Health Survey as a proxy measure for a healthy diet and correlates reasonably well with more compre‐hensive dietary assessments such as the Healthy Eating Index. Measurement of clustering Correlation between risk factors does not necessarily imply clustering. Rather, clustering exists when the observed distribution of the risk factors differs from that expected assuming the risk factors to be independent of each other. The expected joint prevalence of any set of risk factors is simply the product of the individual risk factor prevalences. For example, if the prevalence of smoking is 20% and the prevalence of drinking is 30%, then by the laws of probability the expected joint prevalence of [smoking + drinking] is 6%. If the observed prevalence exceeds the expected prevalence, clustering is said to occur. Analytical approach First, the observed prevalence of each singular behaviour and of all possible behavioural patterns (co‐occurrences of behaviours) is briefly described. Second, the association of each behavioural pattern with socio‐demographic variables is analysed by multiple logistic regression modelling. The model adjusts for age (in four categories: 15–24, 25–44, 45–64, 65+), sex, ethnicity (three categories as indicated above) and deprivation as a measure of socio‐economic position (five categories: quintiles of the NZDep2001 deprivation index, 1 being least deprived, 5 being most deprived). NZDep2001 is a Census‐based small area index of deprivation derived by principal component analysis of nine socio‐economic variables included in the 2001 Census. The reference group for the regression models is 25–44 years of age, male, European, deprivation quintile 5. While age is adjusted for in all reported odds ratios, the effect of age is not itself reported as this is biased by the exclusion of survey respondents with diagnosed cardiovascular disease or cancer. Finally, clustering (Observed/Expected prevalence ratio) is analysed for each behavioural pattern separately by socio‐demographic subgroup (i.e. a stratified analysis). Confidence intervals for the O/E or ‘clustering’ ratios were estimated by standard parametric methods for Poisson random variables. For all analyses, the prevalence or clustering of both healthy and unhealthy behaviours is reported. These are not mirror images of each other, because unhealthy behaviours are typically less prevalent than their healthy counterparts – so higher degrees of clustering are typically found for the former (since clustering is defined as a ratio measure). While this could be corrected by normalisation (re‐scaling), this has not been done since it is the actual degree of clustering that is important rather than the comparison of clustering of healthy compared with clustering of unhealthy behaviours. Prevalence rates have been age standardised to the World Health Organization (WHO) World Population by the direct method, and ethnicity standardised to the New Zealand 2001 Census population, where relevant. Ethnic standardisation is intended to enable comparison of degrees of clustering by deprivation level unconfounded by ethnicity. By contrast, comparison of clustering by ethnicity does not require standardisation for deprivation because deprivation is a mediator, not a confounder, of the ethnicity/outcome relationship. Results Descriptive epidemiology Healthy behaviours Table 2 shows the observed prevalence of single healthy behaviours in the New Zealand adult (15+) population, as well as the prevalence of a ‘healthy lifestyle’. Details of all healthy behavioural patterns are shown in Table 6 . 2 Healthy behaviour prevalence rates. Number a Prevalence (%) Non‐smoking Healthy drinking Physically active Healthy diet Healthy lifestyle b All (crude) 10,223 76.3 81.1 75.3 54.0 29.4 Age 15–24 1,517 73.2 67.1 76.1 44.9 20.5 25–44 4,664 72.4 80.5 74.5 51.9 26.2 45–64 2,918 80.0 87.9 78.6 60.0 36.8 65+ 1,124 90.2 94.7 66.8 66.7 41.9 Sex Male c 3,961 75.1 70.9 80.4 44.3 22.4 Female c 6,262 77.1 87.6 71.1 61.9 34.5 Ethnicity Maori c 3,406 50.4 71.2 77.0 49.5 18.6 Pacific c 819 67.3 80.8 67.2 38.4 15.9 Other c 5,998 79.8 80.5 75.9 54.7 30.6 SES Dep Q1 d 1,389 83.6 82.0 79.4 57.2 34.1 Dep Q2 d 1,300 81.4 79.6 77.0 59.3 33.2 Dep Q3 d 1,518 79.0 80.6 76.4 55.6 30.3 Dep Q4 d 1,950 72.4 78.7 74.1 49.1 23.8 Dep Q5 d 4,066 64.0 76.7 71.0 45.8 22.4 Notes: (a) Number of respondents included in analysis. (b) Healthy lifestyle = all four behaviours reported. (c) Age standardised. (d) Age and ethnicity standardised. 6 Clustering of healthy behaviours. S‐A‐P‐D S‐A‐P S‐A‐D S‐P‐D A‐P‐D All (crude) Observed 29.4 48.7 38.5 34.0 35.0 Expected 25.2 46.6 33.4 31.0 33.0 Ratio 1.17 a 1.05 a 1.15 a 1.10 a 1.06 a 15–24 years Observed 20.5 40.3 25.7 28.0 24.7 Expected 16.8 37.4 22.1 25.0 22.9 Ratio 1.22 a 1.08 a 1.17 a 1.12 a 1.08 25–44 years Observed 26.2 45.4 35.5 30.2 32.6 Expected 22.5 43.4 30.2 28.0 31.1 Ratio 1.16 a 1.05 a 1.17 a 1.08 a 1.05 a 45–64 years Observed 36.8 57.1 45.9 41.1 42.9 Expected 33.2 55.3 42.2 37.7 41.5 Ratio 1.11 a 1.03 1.09 a 1.09 a 1.03 65+ years Observed 41.9 57.9 59.0 43.6 45.4 Expected 38.1 57.1 57.0 40.2 42.2 Ratio 1.10 a 1.01 1.04 1.08 1.08 Male b Observed 22.4 45.8 27.4 29.0 26.7 Expected 19.0 42.8 23.6 26.7 25.3 Ratio 1.18 a 1.07 a 1.16 a 1.08 a 1.06 Female b Observed 34.5 50.0 46.6 37.9 40.9 Expected 29.7 48.0 41.8 33.9 38.6 Ratio 1.16 a 1.04 a 1.11 a 1.12 a 1.06 a Maori b Observed 18.6 30.6 22.6 23.2 30.2 Expected 13.7 27.6 17.8 19.2 27.1 Ratio 1.36 a 1.11 a 1.27 a 1.21 a 1.11 a Pacific b Observed 15.9 42.1 22.9 17.9 22.0 Expected 14.0 36.5 20.9 17.4 20.9 Ratio 1.13 1.15 a 1.10 1.03 1.06 Other b Observed 30.6 50.4 39.9 35.8 35.2 Expected 26.7 48.8 35.1 33.1 33.4 Ratio 1.15 a 1.03 a 1.14 a 1.08 a 1.05 a Quintile 1 c Observed 34.1 55.1 42.4 39.1 38.5 Expected 29.4 52.2 37.2 36.5 35.9 Ratio 1.15 a 1.03 1.11 a 1.07 1.06 Quintile 2 c Observed 33.2 51.0 42.6 38.1 38.7 Expected 28.5 49.9 37.3 35.8 35.5 Ratio 1.15 a 1.04 1.13 a 1.06 1.09 Quintile 3 c Observed 30.3 48.4 39.9 35.4 35.6 Expected 26.5 47.9 34.7 33.1 33.8 Ratio 1.14 a 1.01 1.14 a 1.07 1.05 Quintile 4 c Observed 23.8 44.3 32.3 28.9 29.0 Expected 20.8 42.3 28.0 26.5 28.6 Ratio 1.14 a 1.04 1.15 a 1.09 a 1.01 Quintile 5 c Observed 22.4 40.5 29.3 27.4 28.0 Expected 17.1 35.5 23.9 22.7 26.0 Ratio 1.31 a 1.14 a 1.22 a 1.21 a 1.08 a Notes: (a) p value <0.05. (b) Age standardised. (c) Age and ethnicity standardised. S=non smoking; A=healthy drinking; P=sufficient physical activity; D=healthy diet. Overall, 76% of New Zealand adults are non‐smokers, 81% have a healthy drinking pattern, 75% are sufficiently physically active for health, and 54% consume a healthy diet (as indexed by sufficient fruit and vegetable intake). However, this overall assessment disguises substantial variations between population subgroups, with older people more likely to exhibit healthy behaviours (except for physical activity) than youth; females than males (again except for physical activity); European/Others than Maori or Pacific people; and deprivation quintile 1 (the least deprived) than quintile 5 (the most deprived). Almost 30% of adults report a healthy lifestyle (as defined). However, this again varies with age, from 20% in youth to more than 40% in older people. It also varies with sex, being higher in females (35%) than males (22%) after standardising for age. Maori and Pacific ethnic groups have lower prevalence of the healthy lifestyle (19% and 16% respectively) than European/Others (31%), adjusting for age but not deprivation. A socio‐economic gradient was found, with the prevalence of the healthy lifestyle varying from 34% in deprivation quintile 1 (least deprived) to 22% in quintile 5 (most deprived), adjusting for age and ethnicity. Unhealthy behaviours Table 3 shows the observed prevalence of single unhealthy behaviours in the New Zealand adult (15+) population, as well as the prevalence of unhealthy lifestyle. Detailed prevalences of all unhealthy behavioural patterns are shown in Table 7 . 3 Unhealthy behaviour prevalence rates. Number a Prevalence (%) Smoking Unhealthy drinking Insufficiently active Unhealthy diet Unhealthy lifestyle – all 4 behaviours Unhealthy lifestyle – any 3 of 4 behaviours All (crude) 10,223 23.7 18.9 24.7 46.0 1.4 13.6 Age 15–24 1,517 26.8 32.9 23.9 55.1 3.3 22.9 25–44 4,664 27.6 19.5 25.5 48.1 1.4 14.8 45–64 2,918 20.0 12.1 21.4 40.0 0.5 7.9 65+ 1,124 9.8 5.3 33.2 33.3 Sex Male b 3,961 24.9 29.1 19.6 55.7 1.8 17.2 Female b 6,262 22.9 12.4 28.9 38.1 1.4 11.8 Ethnicity Maori b 3,406 49.6 28.8 23.0 50.5 2.4 26.3 Pacific b 819 32.7 19.2 32.8 61.6 4.0 28.1 Other b 5,998 20.2 19.5 24.1 45.3 1.4 12.1 SES DepQ1 c 1,389 16.4 18.0 20.6 42.8 d d DepQ2 c 1,300 18.6 20.4 23.0 40.7 1.0 11.5 DepQ3 c 1,518 21.0 19.4 23.6 44.4 0.7 10.0 DepQ4 c 1,950 27.6 21.3 25.9 50.9 1.3 15.1 DepQ5 c 4,066 36.0 23.3 29.0 54.2 3.3 25.9 Notes: (a) Number of respondents included in analysis. (b) Age standardised. (c) Age and ethnicity standardised. (d) Count suppressed (<10). 7 Clustering of unhealthy behaviours. S‐A‐P‐D S‐A‐P S‐A‐D S‐P‐D A‐P‐D All (crude) Observed 1.4 2.0 5.0 4.0 2.6 Expected 0.5 1.1 2.1 2.7 2.1 Ratio 2.75 a 1.81 a 2.43 a 1.49 a 1.21 a 15–24 years Observed 3.3 4.2 8.8 5.5 4.4 Expected 1.2 2.1 4.9 3.5 4.3 Ratio 2.84 a 1.99 a 1.81 a 1.56 a 1.02 25–44 years Observed 1.4 2.0 5.5 4.4 2.9 Expected 0.7 1.4 2.6 3.4 2.4 Ratio 2.12 a 1.46 a 2.12 a 1.30 a 1.21 a 45–64 years Observed 0.5 0.9 2.9 2.9 1.2 Expected 0.2 0.5 1.0 1.7 1.0 Ratio 2.41 1.74 a 3.00 a 1.69 a 1.16 65+ years Observed – – – 1.7 1.3 Expected – – – 1.1 0.6 Ratio – – – 1.57 2.22 a Male b Observed 1.8 2.4 7.3 3.7 3.8 Expected 0.8 1.4 4.0 2.7 3.2 Ratio 2.28 a 1.69 a 1.81 a 1.36 a 1.20 a Female b Observed 1.4 2.0 3.5 4.5 1.8 Expected 0.3 0.8 1.1 2.5 1.4 Ratio 4.48 a 2.44 a 3.24 a 1.78 a 1.32 a Maori b Observed 2.4 3.8 10.9 8.0 3.6 Expected 1.7 3.3 7.2 5.8 3.3 Ratio 1.45 a 1.16 1.51 a 1.39 a 1.08 Pacific b Observed 4.0 5.2 8.4 8.7 5.4 Expected 1.3 2.1 3.9 6.9 3.9 Ratio 3.15 a 2.53 a 2.17 a 1.32 a 1.39 a Other b Observed 1.4 1.8 4.5 3.3 2.5 Expected 0.4 0.9 1.8 2.2 2.1 Ratio 3.26 a 1.90 a 2.52 a 1.50 a 1.17 a Quintile 1 c Observed – 1.8 4.8 2.8 2.9 Expected – 0.7 1.5 1.6 1.8 Ratio – 2.57 a 3.20 a 1.75 a 1.64 a Quintile 2 c Observed 1.2 1.7 4.2 2.8 2.8 Expected 0.4 0.9 1.7 1.9 2.0 Ratio 3.10 a 1.83 a 2.46 a 1.41 a 1.41 a Quintile 3 c Observed 0.7 1.0 5.2 2.4 1.4 Expected 0.5 1.0 1.9 2.2 2.1 Ratio 1.40 1.04 2.76 a 1.09 0.70 Quintile 4 c Observed 1.3 2.3 5.3 4.5 3.0 Expected 0.8 1.5 3.0 3.6 2.8 Ratio 1.68 1.51 a 1.80 a 1.24 1.03 Quintile 5 c Observed 3.3 4.3 8.5 8.3 4.8 Expected 1.2 2.4 4.4 5.0 3.6 Ratio 2.75 a 1.77 a 1.94 a 1.66 a 1.33 a Notes: (a) p value <0.05. (b) Age standardised. (c) Age and ethnicity standardised. S=smoking; A=unhealthy drinking; P=insufficient physical activity; D=unhealthy diet. Rates were not calculated when counts less than 10. Overall, 24% of New Zealanders currently smoke cigarettes, 19% exhibit a hazardous drinking pattern, 25% are insufficiently physically active for health, and 46% consume an unhealthy diet (as indexed by inadequate intake of fruit and vegetables). As with the corresponding healthy behaviours, differences are seen with age, sex, ethnicity and deprivation as shown in Table 3 . Turning to the unhealthy lifestyle construct, approximately 15% of the population may be characterised as having an unhealthy lifestyle (defined as any three or all four unhealthy behaviours), although only 1.5% of the population acknowledge all four unhealthy behaviours. The prevalence of an unhealthy lifestyle varies with age (26% in youth, 8% in middle‐aged adults), sex (19% in males, 13% in females, age adjusted), ethnicity (29% in Maori, 32% in Pacific people, 13.5% in Others, adjusting for age) and deprivation quintile (from 13% in quintile 2 to 29% in quintile 5, adjusting for age and ethnicity). Co‐occurrence: regression analysis Healthy behaviours Table 4 summarises the model output for all healthy behaviour patterns (i.e. co‐occurrence, not clustering); two‐behaviour patterns are not shown but are available from the first author on request. 4 Odds ratios and 95% CIs for healthy behaviour patterns. S‐A‐P‐D A‐P‐D S‐P‐D S‐A‐D S‐A‐P Female 1.83 1.91 1.47 2.39 1.18 (1.60–2.09) (1.69–2.16) (1.30–1.67) (2.11–2.71) (1.05–1.34) Maori 0.57 0.89 0.62 0.47 0.47 (0.44–0.73) (0.72–1.09) (0.48–0.79) (0.37–0.59) (0.39–0.57) Pacific 0.52 0.65 0.49 0.50 0.86 (0.39–0.71) (0.48–0.88) (0.36–0.67) (0.38–0.67) (0.64–1.15) Q1 1.83 1.71 1.76 1.81 1.74 (1.41–2.38) (1.34–2.18) (1.35–2.29) (1.41–2.33) (1.39–2.17) Q2 1.84 1.75 1.80 1.84 1.50 (1.42–2.38) (1.37–2.24) (1.38–2.35) (1.42–2.38) (1.20–1.88) Q3 1.55 1.47 1.48 1.63 1.32 (1.21–1.99) (1.16–1.86) (1.16–1.90) (1.29–2.07) (1.05–1.67) Q4 1.10 1.10 1.09 1.17 1.11 (0.85–1.41) (0.88–1.38) (0.86–1.38) (0.91–1.50) (0.89–1.37) Notes: Reference group is male, European/Other, Deprivation Quintile 5. S=non‐smoking; A=healthy drinking; P= sufficient physical activity; D=healthy diet. Two‐behaviour patterns not shown (available from first author on request). Females are almost twice as likely as males to enjoy a healthy lifestyle (odds ratio 1.8). Females also have significantly higher prevalences of all three and two‐behaviour patterns (co‐occurrences) except for the [non‐smoking + sufficient activity] pattern that occurs 20% less often than in males, a difference that is also statistically significant at the 95% level. Maori are less likely than European/Others to exhibit healthy lifestyles and all three‐ and two‐behaviour patterns except for [physically active + healthy diet], for which there is no difference. The results for Pacific people are essentially the same, although not all differences are statistically significant – perhaps due to the relatively smaller numbers in the sample. A clear socio‐economic gradient in the prevalence of healthy lifestyles and all three‐ and two‐behaviour patterns is evident from the deprivation analysis, adjusting for age, sex and ethnicity. Unhealthy behaviours Table 5 summarises the model output for all unhealthy behaviour patterns (i.e. co‐occurrence, not clustering); two‐behaviour patterns are not shown but are available from the first author on request. 5 Odds ratios and 95% CIs for unhealthy behaviour patterns. S‐A‐P‐D A‐P‐D S‐P‐D S‐A‐D S‐A‐P Female 0.67 0.42 1.18 0.42 0.71 (0.42–1.08) (0.29–0.62) (0.86–1.62) (0.32–0.55) (0.48–1.05) Maori 1.48 1.27 1.80 2.44 1.68 (0.67–3.29) (0.69–2.33) (1.17–2.78) (1.68–3.55) (0.84–3.36) Pacific 1.91 1.56 1.53 1.65 2.10 (0.83–4.38) (0.83–2.94) (0.90–2.61) (0.87–3.12) (0.97–4.54) Q1 0.55 0.60 0.31 0.50 0.47 (0.21–1.42) (0.31–1.20) (0.16–0.60) (0.27–0.92) (0.18–1.23) Q2 0.39 0.70 0.31 0.54 0.48 (0.15–1.03) (0.36–1.36) (0.18–0.54) (0.31–0.96) (0.21–1.08) Q3 0.26 0.34 0.31 0.67 0.30 (0.09–0.76) (0.15–0.75) (0.19–0.52) (0.39–1.17) (0.12–0.74) Q4 0.46 0.71 0.56 0.68 0.70 (0.21–1.02) (0.40–1.26) (0.36–0.86) (0.43–1.09) (0.34–1.45) Notes: Reference group is male, European/Other, Deprivation Quintile 5. S=current daily smoking; A=unhealthy drinking; P=insufficient activity for health; D=unhealthy diet (inadequate fruit and vegetable intake). Two behaviour patterns not shown (available from first author on request). Females are less likely than males to show an unhealthy lifestyle, although not all differences are statistically significant. Females are significantly less likely than males to show all of the two‐behaviour patterns except [smoking + insufficient physical activity] (which they are significantly more likely to exhibit) and [unhealthy diet + insufficient physical activity] for which the gender difference is not statistically significant. Confidence intervals for Maori and Pacific ethnic groups are wide, making it difficult to demonstrate significant differences. However, the results are suggestive of higher prevalences for all unhealthy behaviour patterns. Unlike the situation for healthy behaviours, there is less of a clear gradient in unhealthy behaviour patterns across the deprivation quintiles after adjustment for age, sex and ethnicity. There is a tendency, however, for quintiles 1–4, and especially quintiles 1–3, to have lower (sometimes significantly lower) prevalences of all unhealthy behaviour patterns than quintile 5. Clustering: stratified analysis Healthy behaviours Table 6 shows the observed and expected prevalences for all healthy behaviour patterns (except for the two‐behaviour patterns – available from the first author on request), and the corresponding O/E ratios (‘clustering ratios’). Confidence intervals for the ratios are not shown for clarity (available from the first author on request), but those with p values <0.05 are identified. In the total New Zealand population, a small but statistically significant degree of clustering is seen for most healthy behaviour patterns (i.e. the prevalence of co‐occurrence is typically greater than would be expected if the component behaviours were independent). The healthy lifestyle pattern shows the highest degree of clustering (a ratio of 1.17, 95% confidence interval 1.13–1.21). That is, the proportion of individuals exhibiting all four behaviours was 29%, which is 17% higher than the 25% that would have been expected had the four component healthy behaviours been independently distributed across the population. All three‐behaviour patterns show clustering ratios ranging from 1.05 to 1.15. Less clustering is seen for the two‐behaviour patterns, with [non‐smoking + sufficient activity] and [healthy drinking + sufficient activity] showing no clustering at all. Clustering varies with age, with younger age groups showing more clustering than older age groups. Indeed, older people (65+) show no clustering at all except for overall healthy lifestyle (clustering ratio 1.10, 95% CI 1.01–1.20). Few significant gender differences were found after standardising for age. Maori demonstrate higher degrees of clustering of healthy behaviours than do European/Others. Healthy lifestyle has an O/E ratio of 1.36 (CI 1.26–1.46) in Maori compared with only 1.15 (CI 1.09–1.20) in European/Others. Other major differences include [non‐smoking + healthy drinking + healthy diet]: 1.27 versus 1.14; [non‐smoking + sufficiently active + healthy diet]: 1.21 versus 1.08; [non‐smoking + healthy drinking]: 1.10 versus 1.05; and [non‐smoking + healthy diet]: 1.11 versus 1.05 respectively. Little if any difference in the nature or extent of clustering of healthy behaviours is seen across deprivation quintiles 1–4, but quintile 5 displays higher degrees of clustering for some patterns, including the healthy lifestyle pattern itself (1.25 versus 1.11 for quintile 1). Compared with quintile 1, quintile 5 also exhibits substantial clustering in regard to [non‐smoking + sufficiently active + healthy diet]: 1.17 versus 1.05; and [non‐smoking + healthy drinking]: 1.10 versus none (1.00). Unhealthy behaviours Table 7 shows the observed and expected prevalences for all unhealthy behaviour patterns (other than the two‐behaviour patterns, which are available from the first author on request), and the corresponding O/E (‘clustering’) ratios. Confidence intervals for the ratios are not shown for clarity (available from the first author on request), but those with p values <0.05 are identified. For the total New Zealand population, moderate or high degrees of clustering are seen for some patterns (especially the four‐ and three‐behaviour patterns), with slight or no clustering for most of the two‐behaviour patterns. The ‘four behaviour unhealthy lifestyle’ pattern is highly clustered (O/E ratio 2.75, CI 2.29–3.21). Almost as much clustering is found for one of the three‐behaviour unhealthy lifestyle patterns, namely [smoking + unhealthy drinking + unhealthy diet] (clustering ratio 2.43, CI 2.19–2.66). The remaining three‐behaviour unhealthy lifestyle patterns show moderate to slight clustering. One two‐behaviour pattern – [smoking + unhealthy drinking] – also shows a high degree of clustering (ratio 1.79, CI 1.65–1.92). Males and females show the same overall pattern, but the degree of clustering of unhealthy behaviours (when present) is always greater for females than males. For example, the four‐behaviour unhealthy lifestyle pattern has a clustering ratio of 4.48 in females compared with 2.28 in males, after adjusting for age. Other major gender differences are seen with the three‐behaviour pattern [smoking + unhealthy drinking + unhealthy diet]: 3.24 versus 1.81; and the two‐behaviour pattern [smoking + unhealthy drinking]: 2.11 versus 1.57 respectively. There are few differences in the extent or nature of clustering with age, at least to 64 years. Not all behaviour patterns could be assessed in the 65+ age group because of small numbers in some cells. However, it does appear that clustering of the two‐behaviour pattern [smoking + unhealthy drinking] does increase with age, from a clustering ratio of 1.58 in youth to 1.93 in older people. Pacific people show much the same pattern and extent of clustering as European/Others. However, Maori consistently show less clustering of unhealthy behaviours than the other ethnic groups (despite showing more clustering of healthy behaviours). For example, the four‐behaviour unhealthy lifestyle is clustered to an O/E ratio of only 1.45 in Maori versus 3.15 in Pacific people and 3.26 in European/Others. As another example, the [smoking + unhealthy drinking] pattern has a clustering ratio of only 1.26 in Maori (although this is still statistically significant) compared with 1.85 in both of the other ethnic groups. There is very little if any evidence for a gradient in clustering across deprivation quintiles. If anything, for several unhealthy behaviour patterns the degree of clustering tends to be slightly greater in quintiles 1–2 than in the other quintiles. For example, the important two‐behaviour pattern [smoking + unhealthy drinking] has a clustering ratio of 2.26 in Q1, 1.79 in Q2, 1.79 in Q3, 1.67 in Q4 and 1.59 in Q5. Discussion Concept of clustering The concept of clustering is not clearly defined in the literature, and different authors have theorised and operationalised this construct in different ways. An important contribution of this study has been to clarify the definition of clustering as co‐occurrence greater than that expected by chance. Clustering thus implies that the distribution of the risk factors concerned is not independent of each other, but instead reflects a common, more distal, determinant. Thus finding clustering – or not – has both policy and research implications, some of which are elaborated below. Healthy behaviours Our study finds that, in 2002/03, approximately 29% of adult New Zealanders enjoyed a healthy lifestyle characterised by non‐use of tobacco, safe or non‐use of alcohol, sufficient physical activity for health, and a healthy diet as indexed by adequate fruit and vegetable consumption. This is very similar to rates reported for Australia, the United Kingdom and Finland, despite differences between studies in the definitions and thresholds for these health‐related behaviours. It is higher than rates reported for the United States, with better physical activity and fruit and vegetable consumption rates being reported for New Zealand, but again differing definitions make the comparison inexact. While in line with at least some other developed countries, and perhaps higher than many public health workers might have predicted, our results imply that more than two‐thirds of adults are still not meeting even modest thresholds for healthy living. Or more positively, this finding reveals the great scope still available for health gain via improvements in lifestyle. Of even more interest, we found that healthy behaviours show little clustering within individuals. For example, independent distribution of all four health‐related behaviours selected for study would have yielded a joint prevalence of 25% rather than the 29% actually observed – indicating only 17% clustering (i.e. a clustering or observed/expected ratio of 1.17). Even less clustering was found for all the three‐behaviour and two‐behaviour patterns. Such low levels of clustering of healthy behaviours has also been found in other studies. This finding has implications, for example, for research into the health benefits of fruit and vegetable consumption. Such research has often been criticised on the grounds that fruit and vegetable consumption is merely a marker of a healthy lifestyle, so any association between such consumption and health outcomes may be subject to residual confounding by other dimensions of a healthy lifestyle (e.g. non‐smoking, healthy drinking, sufficient physical activity) rather than reflecting a true dietary impact. Our analysis, finding little or no clustering of healthy behaviours within individuals, refutes this hypothesis. Unhealthy behaviours Our study found that, in 2002/03, less than 1.5% of adult New Zealanders exhibited all four of the selected unhealthy behaviours (i.e. daily tobacco use, potentially hazardous alcohol consumption in terms of volume or drinking pattern, insufficient physical activity for health, and inadequate intake of fruit and vegetables as an indicator of wider dietary pattern). Again, this is similar to the rate found in some other developed countries, especially if allowance is made for differences in variable definition, behavioural thresholds, and study design. Using a wider definition of unhealthy lifestyle to include any three as well as all four unhealthy behaviours, then 15% of the adult population would be so categorised. Youth (23%), males (17%), people living in the most deprived 20% of small areas (26%), Maori (26%) and Pacific people (28%) exhibited higher‐than‐average prevalences of these behaviour patterns. For the latter three socio‐demographic groups the proportion with an unhealthy lifestyle was higher than the corresponding proportion with a healthy lifestyle. Turning to clustering, even the low prevalence of the ‘four‐behaviour unhealthy lifestyle’ observed (approximately 1.5%) is almost three times higher than the 0.5% prevalence expected given independent risk factor distributions. The three‐behaviour unhealthy lifestyles show lesser but still substantial degrees of clustering. The two‐behaviour patterns show progressively less clustering than the three‐behaviour patterns with the exception of the co‐occurrence of tobacco and potentially hazardous alcohol consumption, which co‐occurs almost twice as often as expected, a finding that has been reported previously in other countries. Interestingly, insufficient physical activity and unhealthy diet (insufficient fruit and vegetable intake) were not found to cluster to more than a very minor degree – contrary to what might have been hypothesised if physical inactivity contributed substantively to the obesity epidemic. Unlike the situation with healthy behaviours, Maori exhibited less clustering than other ethnic groups for most unhealthy behaviour patterns. While Maori experience higher prevalences of most of the individual risk factors, recent research suggests that unhealthy behaviours – including tobacco use – make a smaller contribution to the ethnic disparity in health than previously estimated. Our study suggests that clustering of unhealthy behaviours makes no contribution to the Maori/non‐Maori health disparity at all. Analogously, it is generally the case that more disadvantaged or lower status groups have higher risk factor prevalences than their more powerful and privileged counterparts, yet differences in the distribution of singular unhealthy behaviours explain relatively little of the socio‐economic gradient in ischaemic heart disease. It has been hypothesised that greater clustering of risk factors might explain more of the gradient, yet our results do not support the notion of a social gradient in clustering of unhealthy behaviours. Health system Our findings on clustering (or lack thereof) of both healthy and unhealthy behaviours are new (for New Zealand) and have implications for health promotion policy and practice both in New Zealand and abroad. Conventional population‐based health promotion programs have tended to focus on single issues, while individual‐based (clinical) services tend towards the case management approach of dealing with multiple factors simultaneously (e.g. absolute cardiovascular risk). The current work supports both these approaches. The relative lack of clustering of healthy behaviours shows that single issue initiatives (e.g. separately promoting fruit and vegetable consumption and walking) are generally appropriate for most universal strategies (because the lack of substantial clustering means that little spin‐off can be expected from one dimension of health to another). Conversely, the clustering of multiple unhealthy behaviours in a relatively small number of people justifies a case management approach to ‘high‐risk’ strategies. Targeted chronic care management and integrated care initiatives emanating from the personal health sector will thus meet – and reinforce – universal public health initiatives coming the other way. Yet three caveats should be borne in mind in using our results for planning either clinical or population‐based preventive interventions. First, exclusion of survey participants with a history of cardiovascular disease or cancer may have introduced bias, especially for older males. It is unlikely, however, that this could have been sufficient to affect our conclusions regarding the extent of clustering. Second, different results may be obtained if different behaviours are selected for study, if those behaviours are defined and operationalised differently, and if different thresholds for categorising the behaviours are chosen. Indeed, our dichotomisation of behaviours represents a major simplification, and a more nuanced approach that recognised varying degrees of behavioural expression (e.g. light, moderate and heavy smoking) might be preferable. Yet contrasts between groups and trends over time in the extent of clustering may still be validly estimated, provided the method is consistently applied. Some analyses have included overweight/obesity (defined via body mass index or waist circumference) in behaviour clustering studies. Given that obesity is not a behaviour per se, we prefer to use measures of physical activity and nutrition directly. Finally, a policy focus on behavioural clustering risks being counterproductive if it decontextualises human behaviour and neglects the social forces that shape behavioural repertoires and their expression in different settings. The lifestyle construct as applied in this study does not imply free and unconstrained behavioural choices by individuals or families. Provided this is understood, we conclude that measurement and monitoring of behavioural clustering can be a useful tool for health promotion, helping to identify intervention points (‘over‐represented’ behavioural patterns within socio‐demographic and geographic subgroups) and evaluate outcomes relating to such intervention points. We have shown that 29% of adults in New Zealand live a relatively healthy lifestyle, being non‐smokers, eating 5+ vegetables and fruit a day, being moderately active, and indulging in non‐harmful use (or non‐use) of alcohol. Conversely, 15% live a relatively unhealthy lifestyle, with any three or all four unhealthy behaviours. There is clearly still much scope for health gain via health promotion. Clustering tendencies were not strong, especially for healthy behaviours, and did not display any social gradient or ethnic disparity. Hence clustering of unhealthy behaviours cannot explain any of the well‐established ethnic or socio‐economic disparities in the burden of chronic disease. Moreover, while a clinical case management approach seems appropriate for the 15% of the population with unhealthy lifestyles, promotion of healthy lifestyles via population‐based programs will need to focus on single issues and little spin‐off from one issue to another can be expected. Acknowledgements We thank the 13,000 New Zealanders who freely gave of their time to participate in the 2002/03 New Zealand Health Survey. This report is published with the approval of the Deputy Director‐General (Public Health). However, opinions expressed are those of the authors and do not necessarily reflect the views of the Ministry of Health or the Counties Manukau District Health Board.

Journal

Australian and New Zealand Journal of Public HealthWiley

Published: Apr 1, 2007

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