Preference and Expectation for Treatment Assignment in a Randomized Controlled Trial of Once- vs Twice-weekly Yoga for Chronic Low Back Pain.

Background: In studies involving nonpharmacological complementary and alternative medicine interventions, participant blinding is very difficult. Participant expectations may affect perceived benefit of therapy. In studies of yoga as treatment for chronic low back pain, little is known about the relationship between patient expectations and preferences on outcomes. This study was designed to identify baseline predictors of preference and to determine if expectations and preferences for different doses of yoga affect back-related function and low back pain intensity. Methods: This was a secondary data analysis of a 12-week randomized controlled trial comparing once-weekly vs twice-weekly yoga for treatment of chronic low back pain in 93 adults from a predominantly low-income minority population. At baseline, participants were asked about back function, back pain, treatment expectations, and treatment preferences. We created a variable “concordance” to describe the matching of participant preference to rand...