Study Results Indicate Daylight Saving Time Has Little Effect on Adverse Cardiovascular Events

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The effects of daylight saving time (DST) on heart health is likely minimal, according to results published in Mayo Clinic Proceedings: Innovations, Quality & Outcomes. The study evaluated the potential connections between DST and serious cardiovascular problems—such as heart attacks and strokes—using a statistical model.¹

"We looked at 5 year [data] across the US, and what we found is that it’s unlikely that there is a clinically meaningful difference in cardiovascular health due to daylight saving time," says lead study author Benjamin Satterfield, MD, PhD, cardiovascular diseases fellow, in a press release.¹

A total of 36,116,951 adults aged 18 years and older across the US—with the exception of Arizona and Hawai’i because these states do not observe DST—were observed during the week directly after the spring and fall DST transitions, when clocks are set an hour forward and backward, respectively. The number of adverse cardiovascular events recorded during the DST transition and control weeks (2 weeks before and after DST) was 74,722—an average increase of approximately 3% and 4% on Monday and Friday of the spring DST transition, respectively—with events being documented when a participant was hospitalized due to a primary diagnosis of a heart attack, stroke, cardiogenic shock, or cardiac arrest.^1,2

"[The cardiovascular events that were recorded] are common health conditions, so this led to the question of whether this is more than would be expected if this had not followed the daylight saving time transition," says Satterfield in the press release.¹

Further, the results indicated that on the Monday and Friday following the spring DST transition, there was a slight statistical increase in the rates of cardiovascular events compared with control weeks (event rate ratio [ERR, 95% uncertainty interval]: Monday, 1.03 [0.97-1.10]; Friday, 1.04 [0.98-1.12]). In addition, the probability of any increase in ERR during the intervention week when compared with control weeks was approximately 81.2% and 87.8% for Monday and Friday, respectively, with less than 60% for the remaining days; however, the probability of this being moderate to large in size was 3.1% for Monday, 5.7% for Friday, and less than 1% for the remaining days, according to the investigators. They also noted that when taking all of the data into consideration, the increase was not considered clinically significant.^1,2

During the autumn DST transition, the probability of any decrease in adverse cardiovascular event rates was estimated to be less than 46%, with moderate to large decreases being less than 4% across all days. Despite this finding, the probability of the adverse event rates during the intervention rate during control weeks was less than 73%, whereas a moderate to large difference was observed to be less than 30% across all days of the week. The authors note that further research can examine the potential impact of DST on mental health and motor vehicle accidents.^1,2

"When decisions are made about whether to abolish [DST], there is no need to take concerns regarding heart health into account," says senior study author and cardiologist Bernard J. Gersh, MB, ChB, DPhil, in the press release.¹

Reference

1. Mayo Clinic. Study shows daylight saving time has minimal effect on heart health. News release. February 27, 2024. Accessed March 4, 2024.

2. Satterfield BA, Dikilitas O, Van Houten H, Yao X, Gersh BJ. Daylight Saving Time Practice and the Rate of Adverse Cardiovascular Events in the United States: A Probabilistic Assessment in a Large Nationwide Study. Mayo Clinic Proceedings: Innovations, Quality & Outcomes. 2024;8(1):45-52. doi:10.1016/j.mayocpiqo.2023.12.006