A systematic review of all studies in postmenopausal women was performed to establish how oestrogen therapy affects FI. Eight articles were deemed eligible for inclusion following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Their quality was assessed using the Cochrane risk-of-bias tool (RoB-2) and Newcastle-Ottawa quality assessment scale.
One randomised controlled trial (RCT), two cohort studies, one observational and four cross-sectional studies were identified. The RCT showed an improvement in FI with anal oestrogen (p = 0.002), but this improvement was also observed in the placebo arm (p = 0.013) and no difference was seen between these groups. A prospective observational study demonstrated significant improvement with an oestrogen patch (p = 0.004), but had no control group. Conversely, a large prospective cohort study demonstrated an increased hazard ratio of FI with current (1.32; 95% CI, 1.20-1.45) and previous oestrogen use (1.26; 95% CI, 1.18-1.34) compared with non-users.
All studies had a high risk of bias and had conflicting views on the effects of oestrogen on FI in postmenopausal women. This review has identified the need for further research in this area by highlighting the paucity of good research for evidence-based practice. We believe that a further RCT of local oestrogen is mandated to draw a valid conclusion.