BMI modified the association of current smoking with the incidence of hypertension in Chinese population: a 22-year cohort study

BACKGROUND: There was little known on how the interaction effect between obesity and current smoking affected the incidence of hypertension. The aim of this study was to investigate how body mass index (BMI) modified the effect of current smoking on the incidence of hypertension. METHODS: Data were obtained from the China Health and Nutrition Survey (CHNS). According to the WHO recommendations for Chinese people, the normal weight, overweight, and obesity were defined using the BMI cutoff values 18.5 kg/m(2), 23.0 kg/m(2), and 27.5 kg/m, respectively. Current smokers were defined as having smoked at least 100 cigarettes or electronic cigarettes, 20 cigars, or 20 tobacco pipes and other type of tobacco in the last 30 days preceding the survey. Hypertension was defined as systolic blood pressure (SBP)/ diastolic blood pressure (DBP) ≥ 140/90 mmHg, use of anti-hypertensive medications, or a self-reported diagnosis. RESULTS: This study included 12,900 subjects. There were interaction effects between obesity and current smoking in females (P = 0.030) and the 50–59 years group (P = 0.049). Current smoking was a significant predictor of incident hypertension only in the total and female populations with normal weight (HR: 1.119 and 1.274; HR 95% CI: 1.013–1.236 and 1.143–1.415; and P = 0.027 and 0.040, respectively). Stratified by age, current smoking affected the development of hypertension only in the 50–59 years subjects with the normal weight (HR: 1.356; HR 95% CI: 1.084–1.697; and P = 0.008). CONCLUSIONS: Current smoking was a significant predictor of incident hypertension only in the female and middle-age populations with normal weight but not in the overweight and obesity as well as the younger and elder populations.