Smoking in women with chronic vaginal discomfort is not associated with decreased abundance of Lactobacillus spp. but promotes Mobiluncus and Gardnerella spp. overgrowth – secondary analysis of trial data including microbio me analysis

Smoking is considered a risk factor for bacterial vaginosis. It is currently unknown which parameters of the vaginal environment are affected and how smoking triggers the disease.The primary objective is to estimate the effect size of smoking on vaginal pH and the Nugent score in patients with chronic vulvovaginal discomfort prior to the development of episode of vaginosis. The secondary goal is to investigate the effect of smoking on individual microscopic parameters of the vaginal environment and on subjectively reported symptoms of vaginal discomfort.Smoking reported by patients was tested as a predictor, using multivariate logistic and ordinal logistic regression analysis on a dataset from the first visit of a randomized trial NCT04171947, which enrolled patients with intermediate vaginal environment. We tested the primary hypothesis (odds ratio (OR) for vaginal pH > 4.5 and Nugent score > 3 in smokers) at the significance level á = 5%. For exploratory analyses of the effect of smoking on the parameters of the vaginal environment, á was corrected as per Bonferoni.In a cross-sectional sample of 250 women after adjusting for other risk factors, smoking had an impact on the Nugent score (OR = 3.3 (1.3-8.5), P = 0.011), while pH was not affected (OR = 1.2 (0.5-2.8), P = 0.698). Smoking was associated with the prevalence of clue cells (P < 0.000), Gardnerella spp. (P = 0.001) and Mobiluncus spp. (P = 0.001), while the prevalence of Lactobacillus remained unchanged (P = 0.049).Contrarily to common assumptions, vaginal Lactobacillus is not directly affected by smoking, which rather promotes the growth of bacteria of Gardnerella and Mobiluncus spp. Given that other parameters remained unaffected, it appears that smoking leads to vaginal dysbio-sis by creating specific favourable conditions for these two opportunistic pathogens.