Background

Physical activity has been associated with a significant reduction in risk of sudden cardiac death in epidemiological studies, however, the strength of the association needs clarification. We conducted a systematic review and meta-analysis to summarize the available data from population-based prospective studies.
Methods

PubMed and Embase databases were searched for studies of physical activity and sudden cardiac death from inception to March 26th 2019. Prospective studies reporting adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) of sudden cardiac death associated with physical activity were included. A random effects model was used to estimate summary RRs (95% CIs).
Results

Thirteen prospective studies were included in the systematic review. Eight prospective studies with 1193 sudden cardiac deaths among 136,298 participants were included in the meta-analysis of physical activity and sudden cardiac death and the summary RR for highest vs. lowest level of physical activity was 0.52 (95% CI: 0.45–0.60, I2 = 0%, pheterogeneity = 0.72). The association was similar in men and women and among American and European studies. In the dose-response analysis the summary RR was 0.68 (95% CI: 0.55–0.86, I2 = 44%, n = 3) per 20 MET-hours/week. Although the test for nonlinearity was not significant, pnonlinearity = 0.18, there was no further reduction in risk beyond 20–25 MET-hours/week. The summary RR was 0.58 (95% CI: 0.41–0.81, I2 = 0%, pheterogeneity = 0.65, n = 2) for the highest vs. the lowest level of cardiorespiratory fitness.
Conclusion

This meta-analysis suggest that a high compared to a low level of physical activity may reduce the risk of sudden cardiac death in the general population. Further studies are needed to clarify the dose-response relationship between specific subtypes and intensities of physical activity in relation to sudden cardiac death.