The Health Impacts of Daylight Saving Time: A Biannual Shift

Daylight Saving Time (DST) in the United States will end at 2 a.m. local time on November 2, 2025, marking a return to standard time. This biannual clock adjustment, which occurs on the first Sunday of November, is often met with mixed feelings as it provides an extra hour of sleep but also leads to shorter daylight hours in the evening. The transition affects most states, with Arizona and Hawaii opting out of DST entirely.

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Research indicates that the shift from DST to standard time can disrupt individuals' circadian rhythms, which regulate sleep, metabolism, and various physiological processes. Experts from Stanford University have found that the biannual time changes can lead to increased risks of heart disease, obesity, and mental health issues. Dr. Jamie Zeitzer, co-director of Stanford’s Center for Sleep and Circadian Sciences, explains that disruptions to the body's master clock can impair the functioning of various organ systems.

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The spring transition to DST has been linked to more severe health consequences than the fall switch. Studies show an uptick in heart attacks, strokes, and workplace accidents following the spring change. However, the fall transition is not without its own challenges, including mood disturbances and fatigue, particularly for those already struggling with sleep issues.

The Globe and Mail (Toronto)

To mitigate the negative effects of the time change, sleep experts recommend gradually adjusting sleep schedules in the days leading up to the shift. This can include moving bedtime and wake-up times by 15 minutes earlier each day. Additionally, exposure to morning sunlight is crucial for resetting the circadian rhythm, while limiting caffeine intake in the afternoon can further support better sleep hygiene.

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Dr. Michael Breus, a clinical sleep specialist, notes that most people will need about a day to adapt to the time change, similar to adjusting to a new time zone. However, vulnerable populations, such as infants and older adults, may require more time to adjust.

Miami Herald

The debate over the necessity of DST continues, with growing calls for its abolition. Organizations like the American Academy of Sleep Medicine and the National Sleep Foundation advocate for permanent standard time, citing its alignment with human biology and potential health benefits. A YouGov poll from October 2024 revealed that 63% of Americans support eliminating clock changes, while only 17% wish to maintain the current system.

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Legislative efforts, such as the Sunshine Protection Act, which proposed making DST permanent, have stalled in Congress. Former President Donald Trump has also expressed opposition to DST, labeling it as inconvenient and costly.

Daylight Saving Time Ends — Here’s What You Need to Know Before Clocks Fall Back

As the end of DST approaches, individuals are encouraged to prepare for the transition by adjusting their sleep routines and seeking morning light exposure. While the extra hour of sleep may be welcomed, the broader implications of the time change on health and well-being continue to spark debate among experts and the public alike.

Daylight Saving Time Ends — Here’s What You Need to Know Before Clocks Fall Back