The Association between BMI, Smoking, Drinking and Thyroid Disease: A Cross-sectional Study in Wuhan, China

Abstract

Background: There is no clear conclusion on the relationship between thyroid disease and obesity and living habits such as smoking and drinking. In this study, a cross-sectional survey of urban residents in central China was conducted to analyze the association of body mass index (BMI), smoking and drinking with subclinical hypothyroidism (SHO) and thyroid nodules (TNs), and to discuss the potential mechanism between these risk or protective factors and the two diseases.Methods: This study included 1279 participants in 2011 and 2012. Questionnaire survey, laboratory examination and ultrasonic diagnosis were conducted on these participants. Binary logistics regression analysis was used to analyze these factors.Results: Overweight (BMI ≥25kg/m2) was closely related to subclinical hypothyroidism and thyroid nodules in univariate and multivariate logistics regression analysis. Smoking had protective effect on subclinical hypothyroidism and thyroid nodules in univariate logistics regression, while drinking had protective effect on thyroid nodules in univariate logistics regression, but there was no significant difference between smoking and drinking and two kinds of thyroid diseases in multivariate logistics regression analysis. In subgroup analysis, BMI ≥ 25kg/m2 was significantly associated with subclinical hypothyroidism in people with positive thyroid antibodies (OR= 2.221, 95%CI: 1.168-4.184, P=0.015) and smokers (OR= 2.179, 95%CI: 1.041-4.561, P=0.039). Thyroid nodules were significantly associated with thyroid nodules in people over 60 years old (OR= 2.069, 95%CI: 1.149-3.724, P=0.015) and drinkers (OR=3.065, 95%CI: 1.413-6.648, P=0.005). Drinking alcohol has a protective effect on thyroid nodules in smokers (OR=0.456, 95%CI: 0.240-0.865, P=0.016) and people with BMI ≥ 25kg/m2 (OR=0.467, 95%CI: 0.236-0.925, P=0.029). No statistical association was found between smoking and the two thyroid diseases in different subgroups.Conclusion: Obesity is a risk factor for thyroid disease, especially in the elderly and people with positive thyroid autoantibodies. Obesity and metabolic syndrome may be more associated with thyroid nodules than subclinical hypothyroidism. Smoking may be a protective factor for thyroid disease, while drinking is a protective factor for thyroid nodules.