Category: Health
A major new U.S. study is offering reassurance for people who worry that the switch to daylight saving time may sharply raise the risk of heart attacks. Researchers at Duke University School of Medicine, analyzing nearly 170,000 patients over roughly a decade, found no significant increase in heart attacks in the weeks surrounding either the spring or fall clock change.
The study, published in JAMA Network Open, used data from the American College of Cardiology’s Chest Pain MI Registry spanning 2013 to 2022. The researchers compared heart attack timing before and after daylight saving transitions and also used Arizona and Hawaii, which do not observe daylight saving time, as control states.
That scale matters. Earlier studies had suggested a possible short-term rise in cardiovascular events after the spring time shift, but those analyses were smaller. In comments reported by Straight Arrow News, Duke cardiologist Dr. Jennifer Rymer said the dataset is effectively national in scope, covering heart attacks across nearly all U.S. hospitals.
What the latest findings show
The new research found no meaningful association between the clock changes and a spike in acute myocardial infarction. One exception appeared in spring 2020, but that period overlapped with the onset of the COVID-19 pandemic, making it difficult to isolate daylight saving time as the cause.
The findings do not mean sleep is unimportant. In fact, the broader medical literature continues to link poor sleep, irregular schedules and disorders such as sleep apnea with worse cardiovascular outcomes. The American Heart Association has emphasized that healthy sleep is a key part of cardiovascular wellness, while the Centers for Disease Control and Prevention warns that insufficient sleep is associated with elevated risks for heart disease, stroke and other chronic conditions.
Why this matters now
The daylight saving debate has not gone away. In recent years, lawmakers at both the state and federal levels have periodically pushed proposals to end the twice-yearly clock change, often citing health and safety concerns. But this latest study suggests one of the most frequently repeated claims — that the time shift itself triggers a broad surge in heart attacks — may be overstated.
That nuance is important. A one-hour time change may be annoying and may temporarily affect sleep routines, but the newest evidence suggests it does not appear to produce a nationwide wave of cardiac emergencies. At the same time, clinicians say the issue should not distract from a larger public health challenge: chronic sleep deprivation and untreated sleep disorders remain serious, long-term threats.
The bigger health picture
The most useful takeaway for readers may be distinction rather than alarm. Daylight saving time can still leave people groggy, less focused and out of rhythm for a few days. Yet the more consequential cardiovascular risks are likely tied to sustained poor sleep habits, high stress, hypertension, obesity, diabetes and lack of preventive care.
That aligns with guidance from the National Heart, Lung, and Blood Institute, which notes that sleep helps regulate healing, blood vessels, metabolism and blood pressure. In other words, sleep still matters deeply for heart health — just not necessarily in the dramatic, immediate way some daylight saving headlines have implied.
For now, the Duke-led analysis appears to answer a long-running question with the strongest dataset yet available: changing the clocks may mess with your sleep, but it probably is not driving a measurable jump in heart attacks across the United States.
Sources: JAMA Network Open; American College of Cardiology Chest Pain MI Registry; Straight Arrow News; American Heart Association; CDC; NHLBI.
