Placebo Response Rates in Electrical Nerve Stimulation Trials for Fecal Incontinence and Constipation: A Systematic Review and Meta-Analysis

Background: Successful treatments following electrical nerve stimulation have been commonly reported in patients with fecal incontinence and constipation. However, many of these nerve stimulation trials have not implemented sham controls, and are, therefore, unable to differentiate overall treatment responses from placebo. This systematic review aimed to quantify placebo effects and responses following sham electrical nerve stimulation in patients with fecal incontinence and constipation. Material and Methods: A literature search of Ovid MEDLINE, PubMed, EMBASE, and Cochrane databases was conducted from inception to April 2017. Randomized sham-controlled trials investigating the effect of lower gastrointestinal electrical nerve stimulation in fecal incontinence and constipation were included. Pediatric and non-sham controlled trials were excluded. Results: Ten randomized sham-controlled trials were included. Sham stimulation resulted in improvements in fecal incontinence episodes by 1.3 episodes per week (95% CI −2.53 to −0.01, p = 0.05), fecal urgency by 1.5 episodes per week (CI −3.32 to 0.25, p = 0.09), and Cleveland Clinic Severity scores by 2.2 points (CI 1.01 to 3.36, p = 0.0003). Sham also improved symptoms of constipation with improved stool frequency (1.3 episodes per week, CI 1.16 to 1.42, p < 0.00001), Wexner Constipation scores (5.0 points, CI −7.45 to −2.54 p < 0.0001), and Gastrointestinal Quality of Life scores (7.9 points, CI −0.46 to 16.18, p = 0.06). Conclusions: Sham stimulation is associated with clinical and statistically meaningful improvements in symptoms of fecal incontinence and constipation, as well as quality of life scores, highlighting the importance of sham controls in nerve stimulation trials. Noncontrolled studies should be interpreted with caution.