Low BMI and falling BMI predict HIV-associated tuberculosis: a prospective study in Tanzania

Low body mass index (BMI) is a known risk factor for tuberculosis (TB) in people without human immunodeficiency virus (HIV), but there are no prospective studies linking BMI to the risk of HIV-associated TB.

In HIV-infected adults with CD4 counts ≥ 200 cells/μl receiving placebo in a TB booster vaccine trial in Dar es Salaam, Tanzania, we measured BMI at baseline and Year 1, and related baseline BMI and change in BMI to the risk of developing TB.

We documented 92 cases of TB among 979 subjects followed for a mean of 3.2 years. Compared to subjects who did not develop TB, subjects who developed TB had a lower baseline BMI (23.2 vs. 24.6 kg/m(2), P = 0.006), and a greater BMI decline from baseline to Year 1 (-0.4 vs. 0.6 kg/m(2), P < 0.001). In multivariate analyses, baseline BMI was associated with the risk of developing TB (hazard ratio [HR] per kg/m(2) 0.94, 95%CI 0.90-0.99, P = 0.028), as was the change in BMI from baseline to Year 1 (HR per kg/m(2) 0.79, 95%CI 0.71-0.87, P < 0.001). Subjects with a baseline BMI < 17 kg/m(2) were more likely to develop TB (HR 3.72, 95%CI 1.16-12.0, P = 0.028).

Low and falling BMI predict HIV-associated TB.