Urinary tract infections and estrogen use in older women.

OBJECTIVE: To examine the relationship between exogenous estrogen use and risk of clinically diagnosed urinary tract infection (UTI) in older women. DESIGN: A case-control study. SETTING: Two hundred seventy-six general practices. PATIENTS: Cases (n = 3,616) were women, age 50-69 years, with a first recorded UTI in the calendar years 1989 or 1990. Controls (n = 19,162) were matched for age and practice. MAIN OUTCOME MEASURE: Clinical diagnosis of UTI. RESULTS: Women using estrogens for greater than or equal to 1 year had an increased risk of being diagnosed with a UTI compared to non-users, crude odds ratio (OR) 1.9 (95% CI 1.5-2.2). All of this excess risk was observed in women with intact uteri, OR 2.1 (CI 1.7-2.7). Hysterectomized women had no increased risk, OR 1.1 (CI 0.8-1.5). Controlling for diabetes, neurologic deficit, atrophic vaginitis, incontinence, and age did not affect the observed associations. CONCLUSION: Estrogen use is associated with an increased risk of UTI in older women with intact uteri but not in hysterectomized women. This observed differential effect on women with or without uteri may be explained by prescribing biases between these two groups of women, but we lack any evidence to support this conclusion over several alternative possibilities.