Co-occurrence and clustering of tobacco use and obesity in New Zealand: cross-sectional analysis.

OBJECTIVE

To describe the co-occurrence and clustering/aversion of tobacco use and obesity in New Zealand.

METHOD

Data were sourced from the 2002/03 New Zealand Health Survey, a nationally representative household survey that included measured body mass index (BMI) and self-reported smoking status. The association of cigarette smoking, obesity, and the combination of these risk factors with socio-demographic variables was analysed by multiple logistic regression. Clustering/aversion (defined as observed prevalence of [smoking + obesity] > or < expected prevalence, where expected prevalence = prevalence of [smoking] x prevalence of [obesity]) was also estimated.

RESULTS

The joint prevalence of smoking plus obesity in the adult population (15+ years) was 4.5%. However, this was 10% for Maori and 8.5% for deprivation quintile 5. Adjusting for relevant covariates, Maori were twice as likely to have both risk factors as non-Maori. A smooth deprivation gradient was found, with deprivation quintile 1 (least deprived) only one-fifth as likely to have both risk factors as quintile 5 (most deprived). There was no evidence of clustering, and aversion (negative clustering) was demonstrated only for middle-aged adults and for Maori.

DISCUSSION

Since smoking cessation is associated with weight gain, substantial aversion might have been expected across all subgroups, yet this was not found. The most likely explanations are that the extent of weight gain associated with smoking cessation has been overestimated or is often not sustained. Even so, health promotion and clinical interventions need to take the dually exposed population into account, addressing not only the unhealthy behaviours themselves but also the social context in which dual exposure occurs.