Serum vitamin D status and bacterial vaginosis prevalence and incidence in Zimbabwean women

Abstract

BACKGROUND Bacterial vaginosis, a highly prevalent vaginal condition, is correlated with many adverse reproductive outcomes. In some studies, low vitamin D (measured as serum 25-hydroxy-vitamin D, 25(OH)D) has been associated with increased prevalence of bacterial vaginosis. OBJECTIVES We examined the cross-sectional association between vitamin D status and prevalence of bacterial vaginosis, separately for pregnant and non-pregnant women. Using prospectively-collected data, we also characterized the effect of time-varying vitamin D status on incident bacterial vaginosis. STUDY DESIGN We quantified 25(OH)D in stored sera collected quarterly from 571 Zimbabwean women participating in the Hormonal Contraception and Risk of HIV Acquisition Study. The analysis was restricted to women not using hormonal contraception. We characterized associations between vitamin D insufficiency (defined as 25(OH)D ≤30 ng/mL vs. >30 ng/mL) and prevalence of bacterial vaginosis among non-pregnant women at the enrollment visit, and among pregnant women at the first follow-up visit that pregnancy was detected. Among women who were negative for bacterial vaginosis at enrollment (n=380), we also assessed the effect of time-varying vitamin D status on incident bacterial vaginosis. We used the Liaison 25 OH vitamin D total assay to measure 25(OH)D. Bacterial vaginosis was diagnosed via Nugent score. RESULTS At enrollment, prevalence of bacterial vaginosis was 31% and overall median 25(OH)D was 29.80 ng/mL (interquartile range: 24.70-34.30 ng/mL): 29.75 ng/mL (interquartile range: 25.15-33.95 ng/mL) among women with bacterial vaginosis and 29.90 ng/mL (interquartile range: 24.70-34.50 ng/mL) among women without bacterial vaginosis. Among pregnant women, the prevalence of bacterial vaginosis was 27% and overall median 25(OH)D was 29.90 ng/mL (interquartile range: 24.10-34.00 ng/mL): 30.80 ng/mL (interquartile range: 26.10-36.90 ng/mL) among women with bacterial vaginosis and 29.10 ng/mL (interquartile range: 23.80-33.45 ng/mL) among women without BV. Vitamin D levels ≤30 ng/mL were not associated with prevalence of bacterial vaginosis in non-pregnant women (adjusted prevalence ratio: 1.04; 95% confidence interval: 0.81-1.34) or pregnant women (adjusted prevalence ratio: 0.88, 95% confidence interval: 0.51-1.54). Vitamin D levels ≤30 ng/mL were similarly not associated with incident bacterial vaginosis (adjusted hazard ratio: 0.98, 95% confidence interval: 0.73-1.31). Our findings were robust to alternative specifications of vitamin D status including using a cutpoint for vitamin D deficiency of <20 ng/ml vs. ≥20 ng/mL, and modeling 25(OH)D as a continuous variable. CONCLUSION Among reproductive-age Zimbabwean women, insufficient vitamin D was not associated with increased BV prevalence or incidence. Given established associations between BV and poor reproductive outcomes, identification of factors leading to high BV prevalence is urgently needed.

Associations between dietary micronutrient intake and molecular-Bacterial Vaginosis

“…Based on our literature review (See Additional file 1: Table S1), most previous studies examining relationships between micronutrients and BV focused on serum vitamin D. However, study designs were heterogeneous, and results were conflicting. Five studies (1 longitudinal and 4 cross-sectional observational studies) showed an increased risk of BV with low vitamin D [9, 16–18, 20], but three studies (all cross-sectional observational studies) [8, 11, 14] suggested no association, or even a reverse association with low vitamin D. Two randomized controlled trials examined vitamin D supplementation. One showed some benefit in asymptomatic BV [12], while another showed no improvement with symptomatic BV recurrence in vitamin D supplementation [13].…”

Total and Free 25-Hydroxy-Vitamin D and Bacterial Vaginosis in Pregnant African American Women

“…Despite our findings of an association between serum 25(OH)D and BV, the present study did not find an association between frank vitamin D deficiency (defined as serum total 25(OH)D < 20 ng/mL) and the occurrence of BV. A cohort of Zimbabwean pregnant women also failed to find an association with vitamin D deficiency and BV [35]. In contrast, a cross-sectional study of 440 US pregnant, selected to be representative of the racial-ethnic composition of women of reproductive age in the US, did find that total 25(OH)D < 30 ng/mL (a category combining vitamin D insufficiency and vitamin D deficiency) significantly increased the odds of BV [36].…”

“…The study of Zimbabwean pregnant women was the first to examine the association between time-varying vitamin D and BV using cohort data, finding that among women who did not have BV at enrollment, deficient or insufficient vitamin D was not associated with incident BV during follow-up [35]. The present study did find an association with change in 25(OH)D from early to later pregnancy, as a continuous measure but not as a categorical measure, and BV later in pregnancy adjusting for baseline Nugent score and 25(OH)D. Further research is needed to confirm this association in other cohorts with measurement of measures of 25(OH)D at more than a single time point in pregnancy and to understand clinical and behavioural factors that may drive changes in vitamin D concentrations during pregnancy.…”

Serum 25-Hydroxyvitamin D and Risk of Self-Reported Bacterial Vaginosis in a Prospective Cohort Study of Young African American Women

“…23 Studies on the association between vitamin D and BV have had mixed findings. Among pregnant women, one observational study found a null association, 24 but most have found a higher prevalence of BV among those who are vitamin D deficient or insufficient. [25][26][27][28] In addition, a randomized controlled trial (RCT) found a trend of lower rates of BV with increasing doses of vitamin D, although they were nonsignificant.…”