Sex differences in the physiological responses to cardiac rehabilitation: a systematic review

Background Heart disease is one of the leading causes of death in Canada. Many heart disease patients are referred for cardiac rehabilitation, a multidisciplinary outpatient program often consisting of exercise training. Cardiac rehabilitation has been proven to be a successful secondary preventative measure in reducing mortality and improving overall health in heart disease patients, and its completion is important for both sexes as there is growing evidence that women benefit as much as men, if not more, with regard to mortality. It is important to note that previous studies have shown that healthy men and women respond differently to aerobic and resistance training, possibly due to hormones, body composition, autonomic and/or cardiovascular differences. However, evaluating sex differences in the efficacy of standard cardiac rehabilitation programs has not yet been fully explored with many studies investigating clinical or anthropometric data but not physiological outcomes. This systematic review aimed to investigate physiological differences in male and female heart disease patients after cardiac rehabilitation. The inclusion criteria were purposefully broad to encompass many cardiac rehabilitation scenarios, many cardiac disease states, and various program lengths and intensities with the intention of highlighting strengths and weaknesses of the current body of literature.Methods To conduct a synthesis without meta-analysis, a search strategy was generated to examine the relationships between heart disease patients, a supervised exercise program, physiological outcomes, and sex differences. The review was registered (Prospero: CRD42021251614) and the following databases were searched from inception to 19 December 2023: APA PsycInfo (Ovid), CINAHL Complete (EBSCOhost), Embase (Ovid), Emcare Nursing (Ovid), Medline All (Ovid; includes PubMed non-Medline), and Web of Science Core Collection. Eighty-eight studies pertaining to fitness, metabolism, body composition, respiratory function, cardiac function and C-reactive protein underwent data extraction.Results and conclusions Importantly, this review suggests that men and women respond similarly to a wide-range of cardiac rehabilitation programs in most physiological variables. However, many studies discussing maximal oxygen consumption, functional capacity, six-minute walk distances, and grip strength suggest that men benefit more. Further research is required to address certain limitations, such as appropriate statistical methods and type/intensity of exercise interventions.