Baseline risk has greater influence over behavioral attrition on the real-world clinical effectiveness of cardiac rehabilitation

ObjectiveFew studies have examined the correlates of real-world cardiac rehabilitation (CR) effectiveness. The objective of this study was to determine the relationship between baseline risk, behavioral attrition, and the number needed to treat (NNT) associated with CR.Study Design and SettingA retrospective study was conducted among 16,061 CR patients between 1995 and 2011 in Canada. Multiple logistic regression models were derived from patient characteristics and measured baseline risk (individual's risk of death within 3 years) and behavioral attrition (individual's risk of premature dropout). We examined the treatment efficacy of CR among nondropouts using a 20% relative risk reduction. Further sensitivity analyses were performed to assess the robustness of our assumptions. We assumed no efficacy among dropouts.ResultsBoth baseline risk and behavioral attrition were independently associated with NNT, although baseline risk had a stronger association with NNT than behavioral attrition. Increasing age, lower baseline fitness, history of diabetes, hypertension, and greater comorbidities were associated with lower NNT. Being female, living alone, living in the lowest neighborhood income quintile, and greater adiposity were associated with higher NNT.ConclusionThe clinical effectiveness of CR is largely driven by the baseline risk rather than the behavioral attrition of the populations they serve. These findings have implications for risk stratification among those with greatest survival yields and programmatic needs.