Lin HH, et al. - Researchers aimed at conducting 2 population-based cohort studies to assess the relationship between body mass index (BMI), diabetes, and tuberculosis. This analyses revealed a complex and nonlinear relationship between obesity, diabetes, and risk of tuberculosis. Novel therapeutic or preventive strategies could be developed with a better understanding of the interplay between host metabolism and tuberculosis immunology.

Methods

• The two population-based cohort studies involved 167,392 participants.
• BMI and diabetes ascertained at baseline were the the main exposure.
• From Taiwan’s National Tuberculosis Registry, researchers ascertained the occurrence of incident tuberculosis.
• In order to characterize the relationship between BMI, diabetes, and tuberculosis, a causal mediation analysis and a joint effects analysis were performed.

Results

• Incident tuberculosis developed in 491 individuals during a median of >7 years of follow-up.
• Researchers noticed that compared with normal-weight individuals, obese individuals (>30 kg/m²) showed a 67% (95% confidence interval [CI], -3% to -90%) and 64% (31%-81%) reduction in tuberculosis hazard in the 2 cohorts.
• The causal mediation analysis showed that obesity had a harmful effect on tuberculosis mediated through diabetes (0.8% and 2.7% increased odds in the 2 cohorts, respectively) but had a strongly protective effect not mediated through diabetes (72% and 67% decreased odds, respectively).
• Individuals who were simultaneously obese and diabetic, compared with nondiabetic normal-weight individuals, had a lower but statistically insignificant risk of tuberculosis (adjusted hazard ratio, 0.30; 95% CI, .08-1.22).