Body mass index and its dose-response relationship with the incidence and risk of tuberculosis, a population-based cohort study

Background Many pieces of evidence presented the body mass index (BMI) was inversely associated with tuberculosis (TB). BMI was radically changed during the past decades in China. The aim of the study was to evaluate the contemporary relationship between BMI and tuberculosis incident. Methods A population-based prospective cohort included 26 022 community participants was conducted. Three rounds of tuberculosis screening were implemented between June 2013 and December 2015. The main exposure was defined as baseline BMI, and was categorized into 3 levels: underweight (< 18.5 kg/m2), normal (18.5 to 24.0 kg/m2), overweight or obese (≥ 24.0 kg/m2). The active tuberculosis incident in the second or third round screening was the study outcome. The dose-response relationship between BMI and tuberculosis incidence as well as tuberculosis risk were analyzed. Results During the followed up of 2.25 years, 43 cases developed tuberculosis in 44 574.4 person-years. The log-linear dose-response relationship between BMI and tuberculosis incidence was fitted (adjusted R2 = 0.95). In multivariable Cox proportional regression, overweight and obese was associated with a lower risk of incident tuberculosis compared with normal weight (adjusted hazard ratio [aHR], 0.34; 95% confidence interval [CI] 0.14–0.82, p < 0.01), the inverse dose-response association between BMI and tuberculosis risk was characterized by restricted cubic spline. In subgroups analysis, the risk of tuberculosis reduced 78% in overweight or obese (aHR, 0.22; 95% CI 0.05–0.97, p = 0.05) and 64% (aHR, 0.36; 95% CI 0.12-1.00, p = 0.05) compared with normal weight among female and elderly. Conclusion Our study revealed that high BMI was a protective factor in tuberculosis development. Precise dose-response relationship between BMI and the incident tuberculosis, as well as the risk of tuberculosis progression in contemporary Chinese adulthood, will benefit to disease control policy.