To examine the association between urinary phytoestrogens and self-reported urinary incontinence in postmenopausal women in the United States using a large, cross-sectional, population-based cohort survey.

Data were analyzed for 1789 postmenopausal women aged 50 years or older who participated in one of the 2001-2010 cycles of National Health and Nutrition Examination Survey and underwent measurement of 4 isoflavone (soy derived) and 2 lignan (flax derived) phytoestrogens in their urine. Incontinence was defined as self-reported stress, urge, other, or mixed incontinence. Urine phytoestrogen concentrations were examined in weighted, multivariate logistic regression models for association with each of the lower urinary tract symptoms. All models were adjusted for age, body mass index, diabetes, race, smoking, and parity.

Increasing urine concentrations of the lignan phytoestrogen enterodiol was associated with decreased likelihood of urge (odds ratio [OR], 0.92; 95% confidence interval [CI], 0.85-0.99), mixed (OR, 0.90; 95% CI, 0.82-0.98), and other (OR, 0.90; 95% CI, 0.81-0.99) incontinence, whereas increasing urine concentrations of the lignan phytoestrogen enterolactone was associated with decreased likelihood of urge (OR, 0.92; 95% CI, 0.86-0.99) and mixed (OR, 0.91; 95% CI, 0.84-0.99) incontinence. No association was observed between any isoflavone phytoestrogens and types of incontinence.

This study demonstrates that lignan phytoestrogens may have a protective effect against incontinence in postmenopausal women. Prospective clinical and laboratory studies are warranted to investigate the mechanism of this relationship.