No Elevated Heart Attack Risk Linked to Daylight Saving Time Change

As Germany prepares to transition from daylight saving time to standard time, the practice of adjusting clocks by one hour continues to be a topic of public debate. Many individuals report experiencing discomfort or disruptions to their daily routines, often describing the shift as a 'social jetlag.' Despite these concerns and ongoing discussions across Europe about discontinuing the time change, the focus has also turned to potential health effects, particularly regarding cardiovascular events such as heart attacks.

Earlier research, including a widely referenced 2008 study published in a leading medical journal, suggested there might be a slight increase in heart attack incidence following the springtime clock change. The explanation proposed was that sleep deprivation and changes to circadian rhythms could temporarily impact cardiovascular health. Subsequent analyses, including a systematic review published in 2024, echoed similar findings, noting a modest rise in risk during the days immediately after daylight saving time began. However, the studies reviewed displayed considerable variability in their results and methodologies.

Recent evidence, however, challenges the notion of a significant association between clock changes and heart attack occurrence. A newly published cross-sectional study, conducted by researchers at Duke University Hospital and utilizing data from the US-based Chest Pain MI Registry, analyzed over 168,000 hospital admissions between 2013 and 2022. The study focused on the three-week period surrounding the annual time changes in both spring and autumn.

The findings revealed that the percentage of patients experiencing an acute myocardial infarction (heart attack) remained consistent across the weeks before, during, and after the time changes. In the spring, 17.0% of patients presented with a heart attack during the week of the clock change, compared to 16.9% the previous week and 16.7% the week after. Similar trends were observed in the autumn, with percentages ranging narrowly between 16.2% and 16.7% across the three-week span. Furthermore, the study found no significant differences in patient characteristics during these periods, nor were there discrepancies in clinical outcomes following hospitalization.

The researchers emphasized that, as with all retrospective studies, their analysis cannot definitively establish causality. They also highlighted 2020 as an exception, noting that patterns of heart attack incidence diverged, likely influenced by factors related to the COVID-19 pandemic. The study suggests that various external factors--such as seasonal flu outbreaks or respiratory illnesses--may influence heart attack rates during certain times of the year, making it difficult to attribute changes solely to the practice of adjusting clocks.

Overall, the current body of evidence indicates that the transition to and from daylight saving time does not significantly increase the risk of heart attacks. While individuals may experience temporary disruptions to their routines, broader population health impacts, particularly regarding cardiac events, appear to be minimal. The debate about the relevance and effects of time changes is likely to continue, but concerns about substantial cardiovascular risks stemming from the practice are not supported by the latest research.