Effect of Cardiac Rehabilitation Dose on Mortality and Morbidity: A Systematic Review and Meta-regression Analysis

OBJECTIVE: To ascertain the effect of CR dose (i.e., duration x frequency/week; categorized as low [<12 sessions], medium [12-35], or high [≥36]) on mortality and morbidity. PATIENTS AND METHODS: The Cochrane, CINAHL, EMBASE, PsycINFO and MEDLINE databases were systematically searched from inception through November30,2015. Inclusion criteria included randomized or non-randomized studies, with a minimum CR dose ≥4, and presence of a control/comparison group. Citations were considered for inclusion, and data were extracted in included studies independently by 2 investigators. Studies were pooled using random-effects meta-analysis, and meta-regression where warranted(covariates included study quality, country, publication year, and diagnosis).RESULTS: Of 4630 unique citations, 33 trials were included comparing CR to usual care (i.e., no dose).In meta-regression, greater dose was significantly related to lower all-cause mortality (high= -.77, Standard Error [SE]=.22, P<.001; medium=-0.80,SE=0.21, P<.001), when compared to low dose. With regard to morbidity, meta-analysis showed dose was significantly associated with less percutaneous coronary intervention (PCI; high: RR=.65, 95% CI .50-.84, and medium/low: RR=1.04, 95% CI .74-1.48; P=.03).This was also significant in meta-regression (high vs. medium/low=-.73, SE=.20, P<.001). Publication bias was not evident. No dose-response association was found for cardiovascular mortality, all-cause hospitalization, coronary artery bypass graft surgery, or myocardial infarction. CONCLUSION:A minimum of 36 CR sessions may be needed to reduce PCI. Future studies should examine the effect of actual dose of CR, and trials are needed comparing different doses.