Placebo improvement in pharmacologic treatment of menopausal hot flashes: Time course, duration, and predictors

Objectives: To characterize the time course, duration of improvement, and clinical predictors of placebo response in treatment of menopausal hot flashes. Methods: Data were pooled from two trials conducted in the Menopausal Strategies: Finding Lasting Answers to Symptoms and Health network, providing a combined placebo group (n = 247) and a combined active treatment group (n = 297). Participants recorded hot flash frequency in diaries twice daily during treatment (Weeks 0-8) and subsequent follow-up (Weeks 9-11). The primary outcome variable was clinically significant improvement, defined as a 50% or greater decrease in hot flash frequency from baseline and calculated for each week in the study. Subgroups were defined a priori using standard clinical definitions for significant improvement and partial improvement. Clinical and demographic characteristics of the participants were evaluated as predictors of improvement. Results: Clinically significant improvement with placebo accrued each treatment week, with 33% significantly improved at Week 8. Of placebo responders who were improved at both Weeks 4 and 8, 77% remained clinically improved at Week 11 after treatment ended. Independent predictors of significant placebo improvement in the final multivariable model were African American race (odds ratio [OR] = 5.61, 95% confidence interval [CI] = 2.41-13.07, p < .001), current smokers (OR = 2.30, 95% CI = 1.05-5.06, p = .038), and hot flash severity in screening (OR = 1.45, 95% CI = 1.00-2.10, p = .047). Conclusions: Clinically significant improvement with placebo accrued throughout treatment with a time course similar to improvement with active drug. A meaningful number of participants in the placebo group sustained a clinically significant response after stopping placebo pills. The results suggest that nonspecific effects are important components of treatment and warrant further studies to optimize their contributions in clinical care.