Every activity at any intensity counts in cardiovascular prevention in individuals with cardiovascular disease

This editorial refers to ‘Association of accelerometer-derived physical activity with all-cause and cause-specific mortality among individuals with cardiovascular diseases: a prospective cohort study’, by Z. Cao et al., https://doi.org/10.1093/eurjpc/zwae248. Regular physical activity (PA) improves cardiovascular health and longevity.1,2 The first epidemiological evidence on the health benefits of PA originates from the 1950s, in which studies were mostly performed in healthy individuals. In the 1980s, the first studies were published exploring the beneficial effects of PA and exercise in patients with manifest cardiovascular diseases (CVD). Although the beneficial effects on survival were still inconclusive at that time, the first positive effects on functional capacity and disease-related complaints were visible.3 In the past decades, the evidence on the health benefits of PA in individuals with CVD has grown exponentially, indicating that already low amounts of PA yield significant cardiovascular benefits and improve longevity.4,5 Increasing small amounts of PA is especially important in individuals with CVD as they are mostly inactive and sedentary. Therefore, the 2020 ESC Guidelines on sports cardiology and exercise in patients with CVD6 recommend exercise-based cardiac rehabilitation in all individuals with coronary artery disease to reduce cardiac mortality and rehospitalization. However, specific PA guidelines for individuals with CVD to improve health and longevity are largely based on the World Health Organization guidelines for the general population recommending at least 150 min of PA on a moderate intensity. Underlying epidemiological evidence that drives these guidelines is exclusively based on self-reported data. It is well known that questionnaires are vulnerable to measurement error (i.e. overreporting), while information about the intensity, frequency, and duration of activities is less accurate, and unstructured and light-intensity PA are not well captured. Furthermore, emerging evidence suggested that the dose–response relationship with PA is health status dependent, which suggests that previous findings in the general population could not be extrapolated to individuals with established risk factors or disease.1,4 In this issue of the European Journal of Preventive Cardiology, Cao et al.7 examine the association of objectively assessed PA using accelerometers with all-cause and cause-specific mortality among individuals with CVD. The authors additionally explored the association of PA at different intensities. Data of 8024 individuals with pre-existing CVD from the UK Biobank were included in a prospective cohort study design. Pre-existing CVD consisted of ischaemic heart disease, atrial fibrillation, heart failure, and stroke. Habitual PA was measured using wrist-worn accelerometers during a 7-day period. The outcomes all-cause, cancer, and CVD mortality were ascertained from death registries with an average follow-up of nearly 7 years. The authors found a curvilinear association between PA and all-cause mortality, in which 50% of the risk reduction was reached after 1380 min/week of light-intensity PA, 155 min/week of moderate-intensity PA, or 45 min/week of vigorous-intensity PA. The dose–response curves for CVD- and cancer-related mortality were roughly similar, and the results were largely consistent after removing deaths which occurred within the first 2 or 4 years of follow-up. Another interesting finding was that the beneficial effect of PA was more pronounced in females compared with males. This study provides important insights into the health benefits of PA. First, large risk reductions are already found at low amounts of PA, especially for higher PA intensities. This suggests that the health benefits of PA are already reached when individuals with CVD perform less than the current PA guidelines stimulating them to chase feasible PA goals. Second, the health benefits were present for all intensities of PA, but higher risk reductions were reached in a lower amount of time when the intensity of PA was increased. This makes vigorous PA more attractive for individuals with CVD who have time constraints and busy schedules during daily life. On the other hand, light- to moderate-intensity PA could be attractive for individuals who are not capable of performing vigorous PA and for those starting to gradually increase PA levels as lower-intensity PA could be more feasible and easier to implement. Third, this study showed that the shape of the dose–response curves was similar to the previous studies using self-reported measures of PA, but the magnitude of the association tends to be larger.2,4,5 In addition, the main findings are comparable with the studies performed in healthy individuals without developed CVD, but the effect estimates in individuals with CVD seem to be larger.2,4 Current study findings could be used to develop tailored guidelines for individuals with CVD and to help clinicians to encourage their patients to increase their PA levels to improve health and longevity. Despite the important study findings of Cao et al.,7 some limitations should be mentioned. An important limitation of the study is the observational nature of the study, and therefore, randomized intervention studies are necessary to confirm the results. Randomized controlled trials on long-term PA interventions with hard endpoints, such as death, are complicated yet not impossible. Other lifestyle covariates such as diet, alcohol consumption, and sleep were assessed approximately 6 years before the baseline assessments, and lifestyle behaviours could change over time. Physical activity was assessed with wrist-worn accelerometers on the dominant wrist. Physical activity measured on the non-dominant wrist is generally more accurate, and PA movements such as carrying weights or lower body movements like cycling are not captured. Furthermore, other activities behaviours such as sedentary time and sleep were not fully incorporated in the analyses. Moreover, accelerometer cut-points expressed as minutes spent in intensity categories, for example light, moderate, and vigorous as performed in the current study, vary between study populations and may complicate the interpretation of PA data and comparison between studies.8 Thus, cut-point-free metrics, such as intensity gradient and average acceleration, may yield advantages in the future as standardized measures improve the precision and comparability across studies.9 Future studies should aim towards personalized guidelines on all daily activity behaviours (i.e. sleep, sedentary time, standing, and light, moderate, and vigorous PA). The 24-hour activity behaviours are dependent on each other in which any change in one behaviour results in a corresponding increase or decrease in another. Advanced statistical techniques, such as compositional data analyses, could overcome this limitation and combine all these behaviours into one analysis. Finally, individuals with different CVD diagnosis (i.e. ischaemic heart disease, atrial fibrillation, heart failure, and stroke) were combined into one group. Based on the disease aetiology, the magnitude and dose–response curve for the health benefits of PA could be different. Small differences between different CVD subtypes were found, but the sample sizes were relatively small, so future studies with large sample sizes for the different CVD diagnoses are necessary to confirm these findings. In summary, findings from this large-scale study among individuals with CVD strengthens the evidence to promote PA in this population and provides the first step towards tailored guidelines for this patient population using objectively assessed PA. New studies involving objective tools are important to take the next step in this research field since the PA assessment is more accurate and provides more detailed information on PA behaviour which could be deployed to improve and tailor current guidelines. Based on the study findings, individuals with CVD should be encouraged to gradually increase PA levels, especially since already low PA volumes provide large benefits especially when they have a sedentary and inactive lifestyle. Furthermore, this study indicates to further improve PA levels by increasing the intensity as more health benefits could be gained in a more time-efficient manner. The additional benefits (e.g. on fitness) of vigorous PA are partially in line with the findings of other studies, such as randomized controlled trials incorporating high-intensity interval training.10 These novel insights will help us to guide individuals with CVD to gradually increase their PA levels, so that every individual could benefit from a physically active lifestyle. E.A.B. has received funding from the European Commission (European Union) under the HORIZON EUROPE Marie Skłodowska-Curie Actions grant agreement no. 101064851. Not applicable.