Between January 1993 and September 1994, 2,763 women were enrolled in the HERS. At the beginning of the trial, 1,228 participants reported no weekly stress or urge incontinence episodes in the past week, and of these, 1,208 women provided urinary incontinence data for at least 1 follow-up visit. Five hundred ninety-seven (49%) were assigned to hormone therapy, and 611 (51%) were assigned to placebo.
These groups of continent women were comparable at baseline, with the exception that the women assigned to placebo were, on average, 1 year older and correspondingly further from menopause compared with women in the hormone group ().
Baseline Characteristics of Postmenopausal Women Without Incontinence in the Heart Estrogen/progestin Replacement Study
In the hormone therapy group, 1 participant discontinued due to adverse reactions, 58 died, 5 failed to return, and 11 were lost to follow-up for other reasons. In the placebo group, 60 died, 5 failed to return, and 12 were lost to follow-up for other reasons. The compliance rates were 80% in the placebo and 68% in the hormone groups.
During 4 years of treatment, weekly incontinence was reported at least once during follow-up by 382 women (64%) taking hormone therapy and 302 women (49%) taking placebo (P ≤ .001). Weekly urge incontinence was reported by 48% of the hormone therapy group and 36% of the placebo group (P < .001). Weekly stress incontinence was reported by 54% of the hormone therapy group and 38% of the placebo group (P < .001). The difference between treatment groups was evident by the 4-month visit and persisted throughout the treatment period ().
Cumulative percentage of women reporting incident weekly urinary incontinence at each visit.
In the continuation-ratio model, women assigned to hormone therapy had 50% higher odds of reporting urge incontinence compared with those assigned to placebo (P = .001) and 70% higher odds of reporting stress incontinence (P < .001) (). In supplementary analyses we found that the adverse effect on urge incontinence seemed to increase with time (P = .03 for linear trend in the treatment effect). The effects of treatment were unchanged in multivariate continuation-ratio models controlling for age, years since menopause, race, parity, diabetes, and body mass index.
Risk of Developing Urinary Incontinence Among Postmenopausal Hormone Users Compared With Nonusers
In women under 60 years of age (n = 184) the effect of hormone therapy on risk of incontinence was minimally and not significantly elevated (odds ratio [OR] 1.31; 95% confidence interval [CI] 0.85–2.04; P = .23). Of the women age younger than 60 years and assigned to placebo (n = 88), 48% reported weekly incontinence of any type, 32% reported weekly urge incontinence, and 37% reported weekly stress incontinence during the 4 years. The respective proportions of women assigned to hormone therapy who reported incontinence (n = 96) were 59%, 40%, and 48%.
The cumulative percentage of women reporting incontinence by type and treatment group is presented in . Excess risk after 4 years of treatment with hormone therapy was 15% for weekly incontinence of any type, 12% for weekly urge incontinence, and 16% for weekly stress incontinence. Numbers needed to harm were 6.9, 8.6, and 5.9 respectively ().
Risks, Excess Risks, and Numbers Needed to Harm After 4 Years of Hormone Treatment
Of the women who reported urinary incontinence of any type, 23% reported 4 or more episodes per week at least once during follow-up. Eighteen percent and 22% reported 4 or more episodes of urge and stress incontinence, respectively.