Citizen science reveals comorbidities in endometriosis with no shift in vaginal microbiome composition

Endometriosis is a chronic inflammatory condition affecting 2-10% of reproductive-aged women, most commonly presenting with pelvic pain and subfertility. While its impact on reproductive health is increasingly recognized, the vaginal microbiome's role in the pathogenesis of endometriosis is still unclear and a comprehensive map of potential co-occurring conditions remains underexplored. Leveraging data from the Isala citizen-science platform in Flanders (Belgium), we analysed vaginal microbiome profiles obtained through 16S rRNA sequencing and health data from 95 women with self-reported endometriosis and 2,279 without. While no differences were observed in vaginal microbiome composition or diversity, we identified significant associations between endometriosis and polyendocrine metabolic ovarian syndrome (previously named polycystic ovarian syndrome; OR = 2.92, 95% CI 1.71-4.78, p < 0.001), migraine (OR = 3.75, 95% CI 1.38-8.60, p = 0.025), irritable bowel syndrome (OR = 2.57, 95% CI 1.43-4.36, p = 0.008) and dyspareunia (OR = 1.67, 95% CI 1.14-2.40, p = 0.033). These findings suggest that the vaginal microbiome composition plays at most a limited role in endometriosis and highlights how citizen science can effectively complement clinical research by capturing underrecognized comorbidities.