Association between obesity and bacterial vaginosis as assessed by Nugent score

Bacterial vaginosis is 1 of the most common vaginal conditions in the United States. Recent studies have suggested that obese women have an abnormal microbiota reminiscent of bacterial vaginosis; however, few studies have investigated the prevalence of bacterial vaginosis in overweight and obese populations. Moreover, despite the increased prevalence of obesity and bacterial vaginosis in black women, it is not known whether racial disparities exist in the relationship between obesity and bacterial vaginosis.

The objective of this study was to examine the relationship between body mass index and bacterial vaginosis as determined by Nugent score and to determine the influence of race in this context.

We performed a cross-sectional study using patient data and vaginal smears from 5918 participants of the Contraceptive CHOICE Project. Gram-stained vaginal smears were scored with the Nugent method and categorized as bacterial vaginosis-negative (Nugent score, 0-3), bacterial vaginosis-intermediate (Nugent score, 4-6), or bacterial vaginosis-positive (Nugent score, 7-10). Body mass index was determined with Centers for Disease Control and Prevention guidelines, and obese individuals were categorized as class I, II, or III obese based on National Institutes of Health and World Health Organization body mass index parameters. Linear regression was used to model mean differences in Nugent scores; Poisson regression with robust error variance was used to model prevalence of bacterial vaginosis.

In our cohort, 50.7% of participants were black; 41.5% were white, and 5.1% were of Hispanic ethnicity; the average age of 25.3 years old. Overall, 28.1% of participants were bacterial vaginosis-positive. Bacterial vaginosis was prevalent in 21.3% of lean, 30.4% of overweight, and 34.5% of obese women (P<.001). The distribution of bacterial vaginosis-intermediate individuals was similar across all body mass index categories. Compared with the scores of lean women, Nugent scores were highest among overweight and obese class I women (adjusted mean difference: overweight women, 0.33 [95% confidence interval, 0.14-0.51] and obese women, 0.51 [95% confidence interval, 0.29-0.72]). Consistent with this, overweight and obese women had a higher frequency of bacterial vaginosis compared with lean women, even after adjustment for variables that included race. Among white women, the prevalence of bacterial vaginosis was higher for overweight and class I and class II/III obese white women compared with lean white women, which is a phenomenon not observed among black women and suggests an effect modification.

Overweight and obese women have higher Nugent scores and a greater occurrence of bacterial vaginosis compared with lean women. Black women have a greater prevalence of bacterial vaginosis independent of their body mass index compared with white women.