Do colleagues influence our lifestyle: The matter of smoking, body mass index and leisure-time physical activity?

•The effect of workgroups was examined on three indicators of health behaviours.•Clustering within workgroups regarding smoking, amount smoked and current BMI•No significant workgroup clustering in physical activity or lifestyle changes•Clustering may be due to social learning or selection into and out of workgroups.

ObjectivePrevious research has indicated that health behaviours tend to cluster in social networks, but few have studied the cluster effect in workgroups. We examined the effect of workgroups on current state and change in three indicators of health behaviours (smoking, body mass index (BMI) and physical activity). Further, we examined whether health behaviours of the respondents at group level predicted lifestyle changes.MethodsIn a prospective cohort (n = 4730), employees from 250 workgroups in the Danish eldercare sector answered questionnaires at baseline (2005) and follow-up (2006). Multilevel regression models were used to examine the effect of workgroups.ResultsWorkgroups accounted for 6.49% of the variation in smoking status, 6.56% of amount smoked and 2.62% of the variation in current BMI. We found no significant workgroup clustering in physical activity or lifestyle changes. Furthermore, changes in smoking status (cessation) and weight gain were seen in workgroups with high percentage of smokers and high levels of BMI.ConclusionWe found modest evidence for clustering of some health behaviours within workgroups, which could be due to social learning or selection into and out of workgroups. Future health promotion programmes at worksites should recognize the potential clustering of lifestyle behaviours within workgroups.