Effectiveness of Cranberry Capsules to Prevent Urinary Tract Infections in Vulnerable Older Persons: A Double-Blind Randomized Placebo-Controlled Trial in Long-Term Care Facilities

OBJECTIVES To determine whether cranberry capsules prevent urinary tract infection (UTI) in long-term care facility (LTCF) residents. DESIGN Double-blind randomized placebo-controlled multicenter trial. SETTING Long-term care facilities (LTCFs). PARTICIPANTS LTCF residents (N = 928; 703 women, median age 84). MEASUREMENTS Cranberry and placebo capsules were taken twice daily for 12 months. Participants were stratified according to UTI risk (risk factors included long-term catheterization, diabetes mellitus, ≥ 1 UTI in preceding year). Main outcomes were incidence of UTI according to a clinical definition and a strict definition. RESULTS In participants with high UTI risk at baseline (n = 516), the incidence of clinically defined UTI was lower with cranberry capsules than with placebo (62.8 vs 84.8 per 100 person-years at risk, P = .04); the treatment effect was 0.74 (95% confidence interval (CI) = 0.57-0.97). For the strict definition, the treatment effect was 1.02 (95% CI = 0.68-1.55). No difference in UTI incidence between cranberry and placebo was found in participants with low UTI risk (n = 412). CONCLUSION In LTCF residents with high UTI risk at baseline, taking cranberry capsules twice daily reduces the incidence of clinically defined UTI, although it does not reduce the incidence of strictly defined UTI. No difference in incidence of UTI was found in residents with low UTI risk.