Effect of Vitamin D Supplementation on Urinary Incontinence in Older Women: Ancillary Findings from a Randomized Trial.

ABSTRACT Background Observational studies among older women have associated vitamin D insufficiency with greater prevalence and incidence of urinary incontinence than older women with adequate vitamin D status. Less is known about the effect of vitamin D supplementation on reducing incontinence. Objective To evaluate the effects of vitamin D supplementation for reducing urinary incontinence frequency in older women. Study Design We conducted an ancillary study of women aged 55 years and older in the Vitamin D and Omega-3 Trial (VITAL), a randomized trial with a 2 × 2 factorial design. Recruitment was from 2011 to 2014, across 50 US states, and follow-up ended January 2018. Randomized treatments in the parent study included: 1) vitamin D3 (cholecalciferol) at a dose of 2000 IU/day, 2) marine omega-3 fatty acids at a dose of 1 g/day, or matching placebo. For this ancillary study, we analyzed women according to their randomization to vitamin D supplementation or placebo, regardless of treatment with omega-3 fatty acid supplementation. Validated urinary incontinence frequency questions were added in year 2 and repeated in year 5 at the trial close. Pre-specified ancillary outcomes included the prevalence of urinary incontinence at year 2 and at year 5, along with incident incontinence and progression of incontinence (from lower to higher frequency) from year 2 to year 5. Pre-planned subgroup analyses examined these outcomes in women with low pre-randomization serum levels of vitamin D [25(OH)D Results Among the 11,646 randomized women who provided urinary incontinence data at year 2 and 10,527 at year 5, the mean age was 70 years at Year 2, with 29% racial/ethnic minorities. The prevalence of urinary incontinence that occurred at least weekly was 29% at year 2 that increased to 37% at year 5. Supplementation with vitamin D compared to placebo was not associated with lower odds of urinary incontinence occurring at least weekly at year 2 (OR 1.08, 95% CI 0.99-1.19) or year 5 (OR 1.04, 95% CI 0.94-1.15). Supplementation with vitamin D compared to placebo was not associated with lower incidence or progression of urinary incontinence from year 2 to year 5: incidence (OR 1.06, 95% CI 0.83-1.35) or progression (OR 0.94, 95% CI 0.82-1.08). Women with low pre-randomization levels of vitamin D (n=836) did not have lower odds of urinary incontinence prevalence, incidence, or progression. Findings were null in subgroups according to incontinence type, obese women, and African American women. Only healthy weight women randomized to vitamin D compared to placebo had lower odds of urinary incontinence progression (OR 0.78, 95% CI 0.63, 0.95 P=0.01). Conclusions Vitamin D supplementation for two to five years was not associated with differences in urinary incontinence prevalence, incidence, or progression compared to placebo for older women with and without adequate serum vitamin D levels, with inconsistent differences among subgroups. Findings do not support broad use of moderate dose vitamin D supplementation for the reduction of urinary incontinence in older women.