A prospective cohort study of the association between body mass index and incident bacterial vaginosis

Some studies suggest that higher body mass index is associated with increased susceptibility to bacterial vaginosis (BV), but results are conflicting. Methods Female sex workers aged 16 to 45 years and participating in an open, prospective cohort study in Mombasa, Kenya between 2000 and 2014 were included in this analysis. Up to 2 years of follow-up were included per woman. Body mass index (BMI) was categorized as underweight (≤18.5), normal (18.5-24.9), overweight (25-29.9), and obese (≥30). Bacterial vaginosis was assessed using Nugent scores. Generalized estimating equations were used to estimate relative risks of the association between BMI and BV. Results At baseline, 32.1% (n = 625) of 1946 women had BV. Half of women were overweight (31.1%, n = 606) or obese (20.1%, n = 391). Participants contributed 14,319 follow-up visits. Adjusting for age, compared to women with normal BMI, overweight (adjusted relative risk, 0.91; 95% confidence interval, 0.81-1.02) and obese (adjusted relative risk, 0.82; 95% confidence interval, 0.71-0.94) women were at lower risk for BV (joint P = 0.03). Conclusions Obese women had a nearly 20% lower risk of BV compared with women with normal BMI. Potential mechanisms for this effect, including possible effects of diet, obesity-associated changes in the gut microbiome, and systemic estrogen levels, should be explored.