Abstract
Objectives: Equol, a gut-derived metabolite of soy isoflavones with estrogenic activity, may influence bladder aging. However, the association between overactive bladder (OAB), which is closely linked to bladder aging, and the estrogenic effects of equol remains unknown. Therefore, this study investigated the association between endogenous equol production and onset and severity of OAB in postmenopausal women. Methods: The study included 128 postmenopausal women, newly diagnosed with OAB, who were categorized into equol- and non-equol-producing groups based on urinary equol levels as measured by enzyme-linked immunosorbent assay. Patient clinical characteristics, OAB Symptom Score (OABSS), and urodynamic parameters were assessed. Propensity score matching was performed to minimize confounding factors related to the timing of lower urinary tract symptom (LUTS) onset. Results: Equol producers exhibited a significantly later onset of LUTS than non-producers (68.7 ± 10.9 vs. 62.7 ± 10.7 years, p = 0.002). Equol producers were more prevalent in the late-onset group (58.6% vs. 31.0%, p = 0.002), which had significantly higher urinary equol concentrations than the early-onset group (p = 0.014). No significant differences were observed in total OABSS or subscale scores between the groups, suggesting that equol did not affect symptom severity. Propensity score-matched analysis (n = 104) confirmed that equol non-production was an independent risk factor for early-onset LUTS (OR, 1.930; 95% CI, 1.248-4.049; p = 0.014). Conclusions: Endogenous equol production was significantly associated with the delayed onset of OAB in postmenopausal women. Thus, equol may serve as a protective factor and non-invasive biomarker to guide individualized prevention and early intervention strategies in urological care for women.