OBJECTIVE: To estimate the association between long-term caffeine intake and risk of urinary incontinence (UI) progression over 2 years among women with moderate UI.
METHODS: We conducted a prospective cohort study in 21,564 women with moderate UI enrolled in the Nurses' Health Study and Nurses' Health Study II. Incontinence progression was identified from questionnaires during 2 years of follow-up. Baseline caffeine intake (ie, average intake during the previous year) and change in caffeine intake during the 4 years before baseline were measured using food frequency questionnaires. Odds ratios (ORs) for incontinence progression according to caffeine intake were calculated for each cohort separately, and then for both cohorts combined.
RESULTS: The percentage of women with UI progression was similar across categories of baseline level of caffeine intake and change in caffeine intake before baseline. For example, percentages were 21% compared with 22% comparing 450 mg or more to less than 150 mg of caffeine per day (adjusted OR 0.87, 95% confidence interval 0.70–1.08). Comparing women with increased caffeine intake to those with stable caffeine intake, percentages with progression were 22% compared with 20% (OR 1.08, 95% confidence interval 0.95–1.22). Results were similar in separate analyses of urge and stress UI.
CONCLUSION: Long-term caffeine intake over 1 year was not associated with risk of UI progression over 2 years among women with moderate incontinence, although we could not examine acute effects of caffeine. Improved understanding of the effect of caffeine on the bladder is needed to better-advise women with incontinence about caffeine intake.
LEVEL OF EVIDENCE: II