Body Mass Index and Asthma in Adults in Families of Subjects with Asthma in Anqing, China

Abstract

We conducted a cross-sectional study of 7,109 adults from families of subjects with asthma in the province of Anhui, China. Asthma was defined either as a combination of physician-diagnosed asthma, airway responsiveness to methacholine at ⩽ 25 mg/ml and two or more respiratory symptoms or asthma attacks (“asthma”); or as a combination of airway responsiveness to methacholine at ⩽ 8 mg/ml and two or more respiratory symptoms or asthma attacks (“symptomatic airway hyperresponsiveness [AHR]”). After adjusting for intensity of cigarette smoking and other variables, both extremes of the body mass index (BMI) distribution were associated with symptomatic AHR in men and women (p < 0.01). In the multivariate analysis, both under- and overweight were associated with asthma in women, and underweight was associated with asthma in men. Among men, those with BMIs of 16 and 30 kg/m² had 2.5 and 2.3 times higher odds of symptomatic AHR, respectively, than those whose BMI was 21 kg/m² (95% CI for OR_{16 vs. 21 kg/m} ² = 1.4 to 3.8; 95% CI for OR_{30 vs. 21 kg/m} ² = 1.2 to 5.0). Among women, those with BMIs of 16 and 30 kg/m² had 2.0 and 2.3 times higher odds of symp- tomatic AHR than those whose BMI was 21 kg/m² (95% CI for OR_{16 vs. 21 kg/m} ² = 1.3 to 3.1; 95% CI_{30 vs. 21 kg/m} ² = 1.2 to 4.5). Among adults in families of subjects with asthma living in rural China, both underweight and overweight are associated with an increased risk of asthma.