Daylight Saving Time Ends November 1, but Doctors Warn of One Surprising Side Effect

Americans will gain an extra hour of sleep when daylight saving time ends Sunday, November 1. But a new warning from the University of Alabama at Birmingham suggests that even this seemingly beneficial clock change can temporarily disrupt the body's internal timing.

The surprising concern isn't losing sleep. It's that the heart, brain, and other organs may adjust to the new schedule at different speeds, creating a brief period of biological misalignment.

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Why an Extra Hour of Sleep Isn't Always Good News

Martin Young, Ph.D., a cardiovascular researcher at UAB, says the body's internal clocks coordinate far more than bedtime.

"We have developed biological rhythms to help synchronize us with these environmental cycles, with the most obvious being sleep-wake cycles," Young explained.

"Many 24-hour biological rhythms are driven by intracellular circadian clocks, which help to orchestrate the timing of cellular functions."

When clocks change, those biological systems don't necessarily reset together.

"Unfortunately, the same is true at a biological level, a loss of temporal synchronization negatively impacts your normal function," Young said.

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What the Clock Change Means for Your Heart

The distinction between spring and fall matters.

According to UAB's October 14 report , gaining an hour in November is associated with approximately 10 percent fewer heart attacks the following Monday, compared with roughly 10 percent more after the spring transition.

That doesn't make the fall change entirely harmless.

Young cautions that disrupted sleep and circadian timing can affect blood pressure, inflammation, blood glucose, and clotting. People with existing cardiovascular disease may be particularly vulnerable to sleep disturbances.

Next: How to Fall Asleep Faster and Stay Asleep, According to Sleep Experts

How to Protect Your Sleep Before November 1

Young recommends gradually shifting bedtime and wake time 15 to 20 minutes later during the two or three days before the transition.

"On each of these mornings, be sure to eat breakfast and get a good dose of sunlight, as both of these factors can help resynchronize your circadian clock," he said.

Limiting nighttime light, moderating caffeine, and maintaining consistent sleep hours can also help.

Bottom line:Don't treat November's extra hour as permission to disrupt your routine. Protect your sleep schedule now, and give your internal clock time to adjust.

Related: What the Science Really Says About Red Light Therapy, Mood, and Seasonal Affective Disorder

This story was originally published by Men's Journal on Oct 17, 2026, where it first appeared in the Health section. Add Men's Journal as a Preferred Source by clicking here.