An elevated risk of urinary tract infections (UTIs) in postmenopausal women has been attributed to an increase in the vaginal pH. Estrogen replacement therapy (ERT) helps restore the vaginal milieu and may have a beneficial effect on risk of infection. Studies examining the association between ERT and UTIs have been inconsistent. We conducted a nested case control study to clarify this relationship in women aged 45–89.
For each case, we selected up to five control women, matched by year of birth. We used pharmacy records to classify women as new users, past users, ongoing users (past and new users), and never users of ERT. There were 254 cases and 1,268 controls.
The risk ratio for UTI was 1.02 [95% confidence interval (CI) 0.74, 1.40] for any use versus never use, after adjustment for health care utilization. The risk ratio for the association between new use and UTI was 1.13 (95% CI 0.46, 2.77). For ongoing users the risk ratio was 1.08 (95% CI 0.76, 1.54), whereas the risk ratio for past use was 0.77 (95% CI 0.39, 1.48).
Our results do not support a protective effect of ERT on the risk of UTIs.