How Daylight Saving Time Increases Overall Health Risks


Recent studies on daylight saving time’s association with increased health risks have heightened the debate on whether to observe the biannual event or switch to one universal time.

With newly introduced legislation and ongoing discussions of abandoning 2 time shifts a year, several experts and industry leaders have considered moving to one universal time. But regarding which time is best for the general public, questions and debates persist.

In 2018, the European Parliament proposed the discontinuation of daylight saving time in response to community displeasure with the time changes.1 

Key Takeaways

  • Scientific research supports that changing the clocks twice a year is detrimental to the general population's health, specifically increasing cardiovascular risk.
  • While many individuals and organizations support the discontinuation of biannual clock changes, opinions seem to be split on which universal time to implement: daylight saving or standard time.
  • Scientists found that permanently implementing standard time will increase morning sun exposure and benefit public health compared with permanent daylight saving time.

“The Parliament solicited the European Commission and the scientific community to conduct an in-depth evaluation and a public survey,” wrote Manfredini et al.1 “The public response strongly supported the discontinuation of biannual clock changes and the European Commission recently proposed their abolition.”

Debates about the abolition of twice-yearly time shifts persist in the United States as well: in March 2022, the Senate unanimously passed legislation, known as the Sunshine Protection Act, that would make daylight saving time permanent starting in 20232; since then, momentum has been lost, the legislation remains stalled, and federal law still prohibits states from enacting permanent daylight saving time.3

Debates on discontinuing daylight saving time shifts persist as permanent legislation still fails to pass. | image credit: irissca -

Debates on discontinuing daylight saving time shifts persist as permanent legislation still fails to pass. | image credit: irissca -

Researchers continue to find evidence that supports the discontinuation of daylight saving time in countries across the globe. As of 2018, about 60 countries worldwide still observed both spring and autumn time changes.1

Daylight Saving Time Vs Standard Time

Daylight saving time is the period starting with the “spring forward” time transition in March and lasts until the second yearly time transition in November. The period from November, when clocks are moved back an hour, to March is known as standard time.4

“[Most people] prefer never having to change the clock again,” wrote Rita Ruben.5 “What they don’t agree on is whether to stay on standard time or daylight saving time permanently.”

In a 2022 CBS News survey, preferences between daylight saving time and standard time were split. Indeed, 46% of participants preferred year-round daylight saving time compared with 33% who preferred year-round standard time, while just 21% favored keeping the biannual time shifts.5

When discussing the public’s preferences of daylight saving or standard time, there is not much of a gray area. People either prefer more sunlight at the start of their day (standard time) or more sunlight at the end of it (daylight saving time).

Despite more survey participants preferring daylight saving time, or more afternoon sunlight, researchers have identified its risk to the misalignment of humans’ internal clocks.

“Morning light plays a critical role in synchronizing our internal clocks and daylight saving time leads to a misalignment between our social clocks (i.e., the clocks on the wall) and our internal clocks, which are synchronized to the sun,” wrote Carter et al.4

With daylight saving time creating more darkness in the morning, authors of the study discussed its effect on children from kindergarten to 12th grade.

During daylight saving time, the sun can rise after 9:00 a.m. in some parts of the country.4 The lack of morning light exposure for children can be related to a decrease in academic performance, which explains why sleep specialists would prefer permanent standard time.4

However, as evident in the Sunshine Protection Act favoring permanent daylight saving time, the debate continues, creating “another clash between scientific evidence and politics.”5

Health Implications of Daylight Saving Time

Biannual time transitions have been attributed to increased risks of cardiovascular health.1,4

“Specifically, the spring shift from standard time to daylight saving time has been associated with an increased risk of myocardial infarction, stroke, and hospital admissions attributed to atrial fibrillation,” wrote the authors of the study4, further enforcing researchers’ preference of permanent standard time.

READ MORE: Poor Sleep in Midlife May Increase Women's Risk of Cardiovascular Disease

Furthermore, scientists found a decrease in myocardial infarction during the first few days of moving the clocks back in November.4 This finding is in line with previous studies claiming that moving the clocks forward in March increases incidences of acute myocardial infarction in the first 2 weeks after the time transition.1

Researchers identified sleep loss as the main cause of circadian misalignment and attributed increased myocardial infarction to the loss of sleep occurring after the March shift to daylight saving time.4

Both the American Academy of Sleep Medicine and Society for Research on Biological Rhythms recently endorsed proposals to move solely to standard time.4 Harvard sleep researcher Elizabeth Klerman, however, said that “this is not just a health issue” and it involves energy, crime, business, government, and communications.5

For long-standing regulations and practices, such as daylight saving time first introduced over 100 years ago5, it’s no surprise to see push back when specific groups aim to discontinue certain practices.

But as conversations move from discontinuing biannual time shifts to the daylight saving-standard time debate, there seems to be hope for one universal observed time. However, this requires agreement on both sides of the scientific and political debate.

“We remain hopeful that there will be a healthy discourse of discussion and debate that our Republic is founded on—let’s get this one right,” concluded the authors in their recommendation to switch solely to standard time.4

READ MORE: Cardiology Resource Center

1. Manfredini, R., Fabbian, F., Cappadona, R., De Giorgi, A., Bravi, F., Carradori, T., Flacco, M. E., & Manzoli, L. (2019). Daylight saving time and acute myocardial infarction: a meta-analysis. Journal of clinical medicine8(3), 404.
2. Shepardson D. US Senate approves bill to make daylight saving time permanent. Reuters. March 16, 2022. Accessed March 8, 2024.
3. Suni E. Latest update: daylight saving time in 2024. Sleep Foundation. Updated March 4, 2024. Accessed March 8, 2024.
4. Carter JR, Knutson KL, Mokhlesi B. Taking to “heart” the proposed legislation for permanent daylight saving time. Am J Physiol Heart Circ Physiol. 2022;323(1):H100-H102. doi:
5. Rubin R. Groundswell grows for permanent daylight saving time, but medical societies overwhelmingly support year-round standard time. JAMA. 2023;329(12):965–967. doi:10.1001/jama.2023.0159
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