Benefits of cardiac rehabilitation following acute coronary syndrome for patients with and without diabetes: a systematic review and meta-analysis

Aim The benefits of cardiac rehabilitation (CR) after acute coronary syndrome (ACS) are well established. However, the relative benefit of CR in those with comorbidities, including diabetes, is not well understood. This systematic review and meta-analysis examined the benefit of CR on exercise capacity and secondary outcomes in ACS patients with a co-diagnosis of diabetes compared to those without. Methods Five databases were searched in May 2021 for randomised controlled trials (RCTs) and observational studies reporting CR outcomes in ACS patients with and without diabetes. The primary outcome of this study was exercise capacity expressed as metabolic equivalents (METs) at the end of CR and >= 12-month follow-up. Secondary outcomes included health-related quality of life, cardiovascular- and diabetes-related outcomes, lifestyle-related outcomes, psychological wellbeing, and return to work. If relevant/possible, studies were pooled using random-effects meta-analysis. Results A total of 28 studies were included, of which 20 reported exercise capacity and 18 reported secondary outcomes. Overall, the studies were judged to have a high risk of bias. Meta-analysis of exercise capacity was undertaken based on 18 studies (no RCTs) including 15,288 patients, of whom 3369 had diabetes. This analysis showed a statistically significant smaller difference in the change in METs in ACS patients with diabetes (standardised mean difference (SMD) from baseline to end of CR: - 0.15 (95% CI: - 0.24 to - 0.06); SMD at the >= 12-month follow-up: - 0.16 (95% CI: - 0.23 to - 0.10, four studies)). Conclusion The benefit of CR on exercise capacity in ACS patients was lower in those with diabetes than in those without diabetes. Given the small magnitude of this difference and the substantial heterogeneity in the results of the study caused by diverse study designs and methodologies, further research is needed to confirm our findings. Future work should seek to eliminate bias in observational studies and evaluate CR based on comprehensive outcomes.