Objective: We aimed to evaluate the hypothesis that the presence of an interaction between smoking and being overweight increases the risks of lifestyle-related diseases (hypertension, diabetes mellitus, dyslipidemia, and cardiovascular disease) in outpatients with mood disorders.
Methods: In this cross-sectional survey, using data from 213 outpatients with mood disorders (95 men, 118 women), we calculated the adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for each of hypertension, diabetes, dyslipedemia, and cardiovascular disease, using a binary logistic regression model; we then calculated the adjusted OR values for smokers and non-smokers with body mass indexes (BMIs) of <25 or ≥25 kg/m². Next, we examined the data for the presence of an interaction between smoking and being overweight, using three measures of additive interaction: relative excess risk due to the interaction (RERI), attributable proportion due to the interaction (AP), and the synergy index (S).
Results: Smokers with BMI <25 kg/m² had a significantly lower risk of hypertension (OR 0.27, 95% CI 0.09-0.81) than non-smokers with BMI <25 kg/m² (reference group). Compared with the reference group, overweight non-smokers had a significantly higher risk (2.82, 1.34-6.19) of hypertension, and overweight smokers had a higher risk (4.43, 1.28-15.26) of hypertension and very high risks of diabetes (8.24, 2.47-27.42) and cardiovascular disease (13.12, 1.95-88.41). The highest RERI was derived from the relation with cardiovascular disease. The highest AP and S were derived from the relation with type 2 diabetes. There was no interaction of smoking and being overweight with dyslipidemia.
Conclusion: The presence of an interaction between smoking and being overweight exacerbates the risks of hypertension, diabetes, and cardiovascular disease in outpatients with mood disorders.