Differences in the association between smoking and relative body weight by level of education

OBJECTIVE: To investigate differences in the association between smoking and relative body weight by sex, age group and level of education. DESIGN: Cross-sectional study. SUBJECTS: About 36 000 men and women who participated in the Monitoring Project on Cardiovascular Disease Risk Factors in the Netherlands in 1987–1991. RESULTS: The association between smoking and relative body weight differed by level of education. This difference was more pronounced among men than among women. Male heavy smokers had statistically significantly (P<0.05) higher mean body mass index (BMI) than never smokers at high educational level, whereas they had a significantly lower mean BMI than never smokers at low educational level. In addition, ex-smokers had significantly higher mean BMI than never smokers in men with high education but not in men with low education nor in women. The difference in the association between smoking and relative body weight by educational level could not be explained by physical activity, fat intake or alcohol consumption nor by factors related to smoking behaviour. CONCLUSION: The association between smoking and relative body weight may differ between subgroups within one population. Therefore adjustment for these subgroups, for example for educational level, may be inappropriate in studies of the BMI-smoking relationship. Also, stopping smoking may have difference effects on weight in these subgroups.