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Most of America will “spring forward” this Sunday for daylight saving time, setting clocks ahead by one hour. While this seasonal shift marks the return of longer daylight hours, the lost hour of sleep can have surprising effects on health.
The Disruptive Effects of Daylight Saving Time
The change in time can disrupt the body’s internal clock, or circadian rhythm, leading to sleep disturbances that may persist for weeks. Studies have shown an increase in heart attacks, strokes, and even fatal car crashes in the days immediately following the time change. The shift in morning darkness and evening light can also impact mental well-being, causing fatigue, irritability, and reduced cognitive function.
When Does Daylight Saving Time Begin?
Daylight saving time starts on Sunday at 2 a.m., when clocks are moved forward by an hour. The switch will be reversed on November 2 when clocks “fall back” to standard time. Hawaii and most of Arizona, along with Puerto Rico, American Samoa, Guam, and the U.S. Virgin Islands, do not observe daylight saving time. Globally, numerous countries implement daylight saving time but follow different start and end dates.
How Lighter Evenings Affect the Brain
The body’s circadian rhythm is largely governed by exposure to natural light. When the sun rises later, morning light exposure is reduced, delaying the body’s natural wake-up signals. Meanwhile, the extended evening light can delay the production of melatonin, the hormone responsible for making us feel sleepy. These changes can lead to sleep deprivation, which is linked to heart disease, cognitive decline, obesity, and other health risks.
The Health Risks of the Time Change
Research has identified a temporary increase in fatal car accidents in the days following the time change, particularly in the morning. The American Heart Association has also highlighted studies that suggest an increase in heart attacks on the Monday after daylight saving time begins, as well as a rise in strokes over the following two days. Experts believe this may be due to the sudden disruption of the circadian rhythm, which can elevate blood pressure and stress hormones in those already at risk.
How to Adjust for Daylight Saving Time
To minimize the impact of the time change, sleep specialists recommend gradually shifting bedtime 15 to 20 minutes earlier in the days leading up to daylight saving time. Exposure to early morning sunlight can also help reset the body’s internal clock. Additionally, adjusting daily routines, such as mealtimes and exercise schedules, can assist in adapting more smoothly. Avoiding caffeine, long afternoon naps, and late-night screen time can further aid in a quicker transition.
Will the U.S. Eliminate the Time Change?
Discussions about ending the time change resurface every year. A bipartisan bill known as the Sunshine Protection Act has been proposed multiple times in Congress, seeking to make daylight saving time permanent. However, major health organizations, including the American Medical Association and the American Academy of Sleep Medicine, advocate for year-round standard time, arguing that it better aligns with human biology and promotes healthier sleep patterns.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Individuals with underlying health conditions should consult a healthcare professional regarding concerns related to daylight saving time adjustments.
© 2025 The Associated Press.
