REGRESSION TO THE MEAN IN FIRST-LINE INTERVENTIONS FOR OSTEOARTHRITIS: AN ILLUSION OF EFFECTIVENESS

Abstract

Purpose: Persons who enroll in osteoarthritis (OA) interventions are likely doing so when experiencing a flare-up in symptoms. Due to the often natural fluctuation of symptoms, this will lead to regression to the mean (RTM), i.e. on average less symptoms at follow-up. In contrast to placebo response, RTM is deceiving as it constitutes no treatment response. Using reported results from two nation-wide exercise and education interventions, we estimated the size of the reported average improvement that is attributable to RTM.