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

Abstract

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.

Figure 1

Participant recruitment and follow-up. ^aDiabetes mellitus or urinary catheter or treated urinary tract infection in past 12 months. ^bNo adherence, withdrawn by elderly care physician or family. ^cIntervention stopped because of end of the study period. UTI = urinary tract infection.

Figure 2

Cumulative incidence of urinary tract infection (UTI) within 1 year of follow-up depending on treatment (cranberry or placebo) stratified for those at low and high UTI risk, accounting for mortality as competing risk. Solid line: cranberry group; dotted line: placebo group. Clinical definition: symptom or positive testing (nitrite test, leukocyte esterase test, dipslide or culture) or antibiotic treatment or UTI reported in the medical record. Strict definition: symptom and positive dipslide or culture.