Health research: Daylight saving time messes with our biological clocks


By Dr. Tim Sandle
March 9, 2025

DIGITAL JOURNAL

Sunset on a summer's day. — Image by © Tim Sandle.

As clocks spring forward for daylight saving time in the U.S., a Virginia Tech expert warns that the time change can have serious health consequences. The research shows that daylight saving time messes with our biological clocks by reducing morning sunlight exposure, which pushes our sleep schedules later and can have negative effects on health.

This is according to Carla Finkielstein, a professor at Virginia Tech’s Fralin Biomedical Research Institute and expert in circadian biology. Circadian rhythm is important in determining sleep and feeding. Daily bio-cycles can alter body temperature, neuronal activity, hormone synthesis, cell regeneration, and other biological activities.

Finkliestein observes: “Staying on standard time year-round is much better for our circadian rhythms, overall health, and well-being.”

Finkielstein’s position is that standard time better aligns with human circadian rhythms. Her lab studies the molecular clocks that tell cells when it’s time to grow, divide, and die. Her research shows that our bodies’ cells have a predictable 24-hour cycle of division regulated by a mix of genetic and environmental cues, such as exposure to light, temperature, and hormone levels.

This research also offers a critical foundation for chronotherapeutics – the study of time-of-day medicine. It also links effects of drugs on biological timing to get the dynamic activity. This new discipline integrates the cellular and molecular biology of circadian rhythms to inform decision-making about when a therapeutic should be administered to yield the best results.

What is daylight saving?

Daylight saving time (DST), began at 2 a.m. on Sunday, March 9, 2025.This is the practice of moving clocks forward one hour in the spring and back by one hour in the fall to extend evening daylight during warmer months. The U.S. daylight saving begins on the second Sunday in March and ends on the first Sunday in November.

It was first adopted in 1918 to conserve energy, it is observed in all states except Hawaii and most of Arizona.

Adverse health effects

Finkliestein’s inference aligns with the Society for Research in Biological Rhythms (SRBR), a scientific organization that warns daylight saving time can increase risks for heart disease, obesity, depression, and workplace accidents.

The SRBR, founded in 1986, advocates for policies that protect biological health, including eliminating DST in favor of permanent standard time.

In 2020, the American Academy of Sleep Medicine published a position statement, aligned with the European Sleep Research Society, European Biological Rhythms Society, and Society for Research on Biological Rhythms’ position, calling for the abolishment of daylight saving time (DST) in favor of the maintenance of standard time year-round.

While many people feel that ending the twice-yearly clock shift is the right thing to do, few people realize that choosing to keep the clocks permanently on DST over standard time could impact their short-term well-being and long-term health.

The organizations have been campaigning on this subject over the past five years. They argue that living with your internal clock slightly offset from the solar light-dark cycle is a form of ‘social jet lag,’ and it has significant consequences, including short sleep duration, increased metabolic disorders, cardiovascular problems, and mood disorders, and even reduced life expectancy.
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