Does daylight saving time lead to more myocardial infarctions?

Background Daylight saving time (DST) is practiced in over 70 countries worldwide. Its assumed economic benefits have become subject of increasing controversy in the recent past, and, together with its likely negative impacts on health, have led to the decision to abolish DST in the EU and the USA. Transitions from and to DST disrupt the circadian rhythm and lead to measurable adverse effects. Among them, the incidence of acute myocardial infarction (AMI) is suspected to increase as a consequence of DST changes. Objective The aim of this study is to examine the relationship between DST transitions and the incidence of acute myocardial infarction based on the available literature. Materials and methods A systematic literature search in the MEDLINE database was performed. Studies were included that observed the AMI incidence after transitioning from or to DST and had a control period beyond or around the post-transitional weeks. Of 26 identified studies, 8 met the inclusion criteria. Results were interpreted with an emphasis on methodological differences, reported incidence rates, and subgroup analyses. Results Seven of the identified studies reported the incidence rate ratio (IRR), observed-to-expected ratio, or odds ratio, while one study only reported IRR values for the individual days and statistical significance levels for the transition weeks. Six studies reported an increased incidence after the spring shift, four of which were statistically significant. Three studies reported an increase after the autumn shift, of which two were statistically significant. Conclusion Several studies show increased AMI incidence rates following both spring and autumn DST shifts, yet results remain in part contradictory. Future research to establish a better understanding of the health implications of DST transitions is warranted, and the quantification of incidence rates should control for confounding factors.