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

Objective — Few 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 Setting — A 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 dropout). We examined the treatment efficacy of CR among non-dropouts using a 20% relative risk reduction. Further sensitivity analyses were performed to assess the robustness of our assumptions. We assumed no efficacy among dropouts.

Results — Both baseline risk and behavioral attrition were independently associated with NNT, though 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 neighbourhood income quintile, and greater adiposity were associated with higher NNT.

Conclusion — The clinical effectiveness of CR is largely driven by the baseline risk rather than behavioral attrition of the populations they serve. These findings have implications for risk stratification among those with greatest survival yields and programmatic needs.