Daylight Saving Time Transitions and Risk of Heart Attack.

Background: The health risks of daylight saving time transitions are intensely debated. Disturbed circadian rhythms and lack of sleep after transitions might increase the risk of acute myocardial infarction (AMI). The only meta-analysis on the risk of AMI has now been considerably expanded.

Methods: In this systematic review and meta-analysis (including meta-regressions and sensitivity analyses), we examine the frequency of AMI in the first few weeks after daylight saving time transitions (OSF registration www.doi.org/10.17605/OSF.IO/7CFKS). Eight databases were searched for pertinent literature up to September 2023. Authors were contacted for additional information. Study quality was rated using the Newcastle-Ottawa Scale.

Results: Twelve studies from ten countries were included in the meta-analysis. Nine were of adequate quality, and three were of good quality. The pooled relative risk (RR) of AMI after daylight saving time onset (spring) was 1.04 (95% confidence interval [1.02; 1.07], I2: 57.3%), and 1.02 ([0.99; 1.05], I2: 51.6%) after daylight saving time offset (autumn). Recalculation after the exclusion of one study with inconsistencies yielded pooled RR values of 1.04 [1.01; 1.06] and 1.00 [0.99; 1.02], with the spring results being heterogeneous (I2: 56.9%) and the autumn results homogeneous (I2: 17.1%).

Conclusion: Current evidence suggests that there may be an increased risk of AMI after the spring transition, although there is moderate to marked heterogeneity among the studies that support this conclusion. More easily interpretable studies, such as those already conducted in the field of economics, should clarify associations with the aid of discontinuity regression and placebo tests. To this end, comparative risk analyses using years or places wherein daylight saving time was not practiced would be suitable.