- Vaginal colonization by beneficial Lactobacillus species is less common in premenopausal Black women than premenopausal white women, but it's unclear whether that difference persists after menopause
- This study involved DNA sequencing of vaginal samples from 44 Black postmenopausal women and 44 white women matched on menopause status and age at screening
- Dominance by Lactobacillus crispatus or L. gasser was significantly more common in Black than white women (27% vs. 5%, P=0.001), but the relative abundance of all Lactobacillus species did not differ significantly in the two groups
- Race is a social rather than biological construct, thus differences in microbiota between racial groups may reflect unmeasured exposures
According to U.S. studies, vaginal colonization by lactobacilli is significantly lower in premenopausal Black women than in premenopausal white women. However, data are lacking on whether this difference is also present in postmenopausal women. The knowledge gap is concerning because the absence of vaginal lactobacilli is associated with HIV infection as well as persistence of human papillomavirus and cervical dysplasia, which increase the risk for cervical cancer.
To investigate, Patricia L. Hudson, MD, former fellow, and Caroline M. Mitchell, MD, of Department of Obstetrics and Gynecology at Massachusetts General Hospital, and colleagues recently sequenced bacterial DNA in vaginal samples from self-identified Black and white postmenopausal women. Black women were significantly more likely than white women to have a vaginal microbial community dominated by Lactobacillus crispatus, but overall there were only small differences between the groups. The findings appear in The Journal of Infectious Diseases.
The research team obtained cervicovaginal samples from the Menopause Strategies: Finding Lasting Answers for Symptoms and Health (MsFLASH) network biorepository. MsFLASH conducted a series of randomized, double-blind, placebo-controlled trials:
- MsFLASH03 (n=75; 32 Black, 43 white) was an eight-week trial of treatment for bothersome vasomotor symptoms in which peri- and postmenopausal women self-collected vaginal swabs
- MsFLASH05 (n=278; 12 Black, 266 white) was a 12-week trial of treatment for vulvovaginal symptoms in which postmenopausal women underwent pelvic exams for collection of vaginal samples
For the current study, the researchers analyzed vaginal samples from the 44 Black participants in the two studies and 44 white participants matched on the study, clinical center, menopause status and age at screening.
- Dominance by L. crispatus or L. gasseri (≥50% of sequences from a given species) was significantly more common in Black than white women (27% vs. 5%, P=0.001)
- Only one individual taxon, L. crispatus, was differentially abundant between the two groups in unadjusted analysis (more abundant in Black women), and the difference was no longer significant when controlling for multiple comparisons
- The relative abundance of all Lactobacillus species in Black and white women was not significantly different overall (89% vs. 51%; P=0.47)
Race Is Only a Proxy
Since race is a social construct, it is difficult to interpret what a "racial" difference in microbiota reflects. However, previous studies have shown the composition of the vaginal microbiota can be influenced by stressful life events, psychosocial stress, perceived stress, lower education level and lower income.
In this study, the Black women had a slightly but significantly worse average score on the Menstrual Quality of Life questionnaire than the white women (4.0 vs. 3.1; P=0.001). They also had higher rates of smoking and were less likely to be college graduates. But all of this should predict a lower abundance of L. crispatus, according to data collected in studies of premenopausal women.
Thus, the findings of this study contradict not only previously established associations between race and vaginal lactobacilli but also the sociodemographic risk factors seen in younger cohorts. These results suggest that differences in microbiota between racial groups may reflect unmeasured exposures for which race is but a proxy.
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