Caffeine intake, and the risk of stress, urgency and mixed urinary incontinence.

PURPOSE Although caffeine consumption is common and generally believed to affect bladder function, little is known about caffeine intake and incident urinary incontinence. MATERIALS AND METHODS We performed a prospective cohort study in 65,176 women 37 to 79 years old without incontinence in the Nurses' Health Study and the Nurses' Health Study II. Incident incontinence was identified from questionnaires during 4 years of followup. Caffeine intake was measured using food frequency questionnaires administered before incontinence development. The multivariate adjusted relative risk of the relation between caffeine intake and incontinence risk as well as attributable risk were calculated. RESULTS Caffeine was not associated with incontinence monthly or more. However, there was a modest, significantly increased risk of incontinence at least weekly in women with the highest (greater than 450 mg) vs the lowest (less than 150 mg) daily intake (RR 1.19, 95% CI 1.06-1.34) and a significant trend of increasing risk with increasing intake (p for trend = 0.01). This risk appeared focused on incident urgency incontinence (greater than 450 vs less than 150 mg daily, RR 1.34, 95% CI 1.00-1.80, p for trend = 0.05) but not on stress or mixed incontinence (p for trend = 0.75 and 0.19, respectively). The attributable risk of urgency incontinence associated with high caffeine intake was 25%. CONCLUSIONS Findings suggest that high but not lower caffeine intake is associated with a modest increase in the incidence of frequent urgency incontinence. A fourth of the cases with the highest caffeine consumption would be eliminated if high caffeine intake were eliminated. Confirmation of these findings in other studies is needed before recommendations can be made.