Cardiac rehabilitation (CR) is a comprehensive program that combines exercise training and lifestyle interventions, and is recommended in patients after an acute coronary syndrome.1 The positive effects of CR on mortality, morbidity, quality of life and psychological well-being are recognized.2 Despite these benefits, some patient subgroups are consistently under-enrolled, including older patients. Participation in secondary prevention programs only reaches around 20% of eligible older patients, and long-term adherence is even worse.3 Besides cardiac disease, aging is associated with increased prevalence of other comorbidities, including musculoskeletal disease, peripheral arterial disease, chronic respiratory disease, cerebrovascular disorders and cognitive impairment,4 which can limit the implementation of exercise-based CR programs. Furthermore, acute disease and hospitalization may aggravate the vulnerability of older patients and contribute to progressive disability. The purpose of this study was to study older patients who attended CR programs and to assess the clinical impact of this intervention in this subgroup compared to younger patients.

Although older patients are under-represented in CR programs, this intervention provides broad benefits in these patients, from metabolic profile and functional capacity to health-related quality of life, as we show in the present study.

Changing body composition, including fat redistribution to central and visceral depots, is a hallmark of the physiological aging process, which has profound effects on health and physical function in older adults. Aerobic exercise appears to slow the age-related accumulation of central body fat and is cardioprotective.9 Although our results showed a neutral effect of CR on BMI, a significant reduction in waist circumference was found in both male and female older patients. Exercise training could contribute, at least in part, to an increase in lean/fat mass proportion, which could explain our results. Curiously, we found that reduction of waist circumference was greater in older female patients compared to their younger counterparts. Similar results were previously found. In 2016, Al Quait and Dohert10 compared CR outcomes of 262813 older (≥65 years) patients to 203012 younger (<65 years) patients and showed a positive correlation between older age and change in body shape risk factors. Regarding waist measurements, older female patients had the best outcomes. Other studies are needed to address this subject, considering all factors of female biology, to understand the impact of exercise training in aging women.

Additionally, in our cohort, the lipid profile of older patients improved, practically reaching the target levels recommended. CR programs have been demonstrated to improve lipid levels, the effect of a combination of exercise training, diet and lipid-lowering therapy.11 Our results suggest that these benefits extend to older patients as well.

We also analyzed changes in EC and cardiac autonomic regulation after exercise training. Although older patients performed worse in exercise testing at both assessment points, their EC improved in the same way as younger patients. The marked improvement in EC that we observed in our older patients agrees with previous reports. Balady et al.12 studied changes in EC following CR programs in patients stratified according to age and gender and found that older patients had lower baseline EC. Similarly, exercise training yielded improvement in exercise tolerance among patients in all age groups, without significant differences between groups.

Although the superimposition of CV disease on age-associated decline in aerobic capacity can result in functional impairment in older patients, exercise-based CR may counteract this effect, which can have prognostic implications. Reports on older patients with and without heart disease have demonstrated a positive impact of exercise training on their outcomes,3 while results from the Cardiovascular Health Study, including 5201 patients with a mean age of 73 years, suggested that level of physical activity is an independent predictor of five-year mortality.13

Cardiac autonomic regulation is also an important focus of interest in coronary patients. It is well known that chronotropic incompetence, usually defined as CI≤80%, is an independent predictor of all-cause death in these patients.14 In patients taking beta-blockers, the threshold for chronotropic incompetence has been reviewed and a cut-off of ≤62% has been proposed.15 In our cohort, nearly all patients were under beta-blocker therapy, which could explain the low baseline CI of both groups. Exercise training have been shown to improve measures of HR variability in patients after infarction.16 The same positive effect could be expected on resting HR, which usually decreases with regular physical activity. Although aging is associated with cardiac neurohormonal dysfunction, a decline in sinoatrial node parasympathetic activity and an increase in sympathetic activity,17 we found that CI and resting HR improved in older patients at the end of the phase 2 CR program, similar to younger patients.

Besides changes in metabolic profile and improvements in functional capacity, there is growing evidence on the impact of CR on quality of life. In the present study, we applied the SF-36 questionnaire to all patients at baseline and at the end of phase 2 of the CR program. Our data showed that, as in younger patients, CR has a positive effect on both the MCS-36 and PCS-36 subscales in older subjects. These findings are in agreement with results from other groups. For instance, Marchionni et al.18 compared CR program outcomes in older and younger patients, and found that the elderly group had significant improvements in all aspects of quality of life studied. Furthermore, Stewart and colleagues19 demonstrated that improved fitness enhances patients’ quality of life and can help older adults to live independently. A routine general psychological assessment of participants, including older subjects, has an important role in a CR program. Simple screening tools can help identify their main problems and can be followed by more sophisticated instruments and referral for treatment as needed. Health-related quality of life assessment not only can have impact on psychosocial well-being, but can also itself be a predictor of mortality, cardiovascular events, hospitalization and costs of care in patients with cardiovascular disease.20 Moreover, considering the role of regular exercise in maintaining mobility, exercise training is an important intervention to reduce or even prevent age-associated disability and can have a marked impact on the daily living needs of older patients. A systematic review of exercise interventions found that multicomponent exercise programs, including endurance, strength, flexibility, and balance training, generally reported significant reductions in disability for older patients. Longer duration of the intervention and follow-up, as well as interventions in more functionally limited individuals, were associated with greater likelihood of benefit.21

As CV risk increases in older population, including higher prevalence of CV risk factors and multivessel coronary disease, as demonstrated in our cohort, the absolute benefit of treatment should increase as well. Perhaps the greatest barrier to the benefits of cardiac rehabilitation in older adults with CV disease is their very low attendance rate in such programs. Practical issues related to the implementation of exercise training programs in older coronary patients include the frequent need for training regimens to be adjusted to accommodate the presence of age-related comorbidities. The least fit individuals are often unable to sustain exercise for long periods and do well starting at very low work levels and repeat intermittent brief bouts of exercise (interval training) that are gradually extended. This can promote progressive fitness, while reducing the potential for overuse injuries.16,22 Beyond their limitations with regard to exercise training, the major contributor to the low utilization of CR by elderly patients is the reluctance of providers to refer them for these programs.23 Many physicians do not recommend CR to their older patients or explain its potential value. Consequently, older adults are less likely to be aware of CR and to pursue options for CR which they do not understand. Additionally, older patients are more likely to live alone and have poor social support, which hampers their attendance at these programs.

This study emphasizes the significant impact of CR programs on the older population, including three aspects of their effects, namely metabolic profile, exercise capacity and health-related quality of life. CR provides an opportunity for longitudinal assessment to address older patients’ issues, redefine optimal management and ultimately improve their outcomes. Increased awareness of physicians, nurses, patients and their families of the benefits of secondary prevention programs like CR will provide a basis for referral and aid the implementation of such programs.

Some study limitations need to be highlighted. This is a retrospective study and selection and referral bias cannot be excluded; however, it represents an application of CR in real-life patient cohorts. Another limitation concerns the assessment of exercise capacity using estimated METs achieved in exercise testing, as opposed to precise measurement with cardiopulmonary gas exchange. Nevertheless, METs have a good correlation with peak oxygen uptake and constitute a valid measure of EC with prognostic value.24 Furthermore, it would be interesting to prolong the follow-up after phase 2 of the CR program to assess whether the effects of CR on metabolic profile, exercise performance and health-related quality of life are maintained over time. Finally, a subgroup analysis of very old patients would also help to determine whether the benefits of CR programs extend to these patients as well.

Current data support the beneficial effects of CR and exercise training in older populations, including improvements in metabolic profile, functional capacity and quality of life indices. This positive impact in older patients was at least similar to that observed in younger counterparts. It is crucial that clinicians strongly and repeatedly encourage older adults to participate in exercise-based CR programs, while carefully considering appropriate and individualized recommendations for exercise prescription.

The authors have no conflicts of interest to declare.