Background: The aim of the study was to examine associations between unhealthy behaviours among the Finnish adult population.
Methods: Data from a series of cross-sectional health behaviour surveys from the years 1991-1998 were pooled. Associations between smoking, alcohol consumption, lack of regular physical activity and unhealthy diet were examined among 22,745 respondents. The associations were first studied in terms of accumulation: the occurrence of each combination of unhealthy behaviours was compared to their expected appearance, assuming that the behaviours were independent from each other. The same associations were then analysed with log-linear models.
Results: Only 2.4% of men and 0.9% of women had all four unhealthy behaviours. Nevertheless, the occurrence of four unhealthy behaviours was about three times more common than expected under the assumption of independence of the behaviours. Also, most of the three-behaviour combinations showed accumulation. Among the pairwise combinations, smoking and alcohol consumption as well as physical inactivity and unhealthy diet showed strongest accumulation, whereas the combination of alcohol consumption and unhealthy diet was less prevalent than expected. The combination of four healthy behaviours appeared 1.3 times more often than expected. In log-linear analysis a model containing all pairwise associations and the three-behaviour interaction between smoking, alcohol consumption and physical inactivity, as well as that of alcohol consumption, physical inactivity and unhealthy diet for men, provided an acceptable fit. Most of the unhealthy behaviours were positively associated but the association between alcohol consumption and unhealthy diet was inverse. Other behaviours modified the strength of the associations. The direction of the association between alcohol consumption and physical inactivity depended on other behaviours.
Conclusions: Unhealthy behaviours showed pairwise and multiple accumulation. No three-behaviour associations were reducible to pairwise associations. Smoking had the strongest and most consistent associations with other unhealthy behaviours. Differences between sociodemographic groups were small and the patterns of unhealthy behaviour were remarkably similar among men and women.