Sep 15, 2025 09:18 PM
https://www.eurekalert.org/news-releases/1097923
INTRO: Every spring, Americans dutifully adjust their clocks forward to daylight saving time, and every fall, back to standard time — but no one seems very happy about it. The biannual time shift is not only inconvenient, it’s also known to be acutely bad for our health. The collective loss of an hour of sleep on the second Sunday in March has been linked to more heart attacks and fatal traffic accidents in the ensuing days.
Now, a study by Stanford Medicine researchers finds there are longer-term hazards as well — and better alternatives.
The researchers compared how three different time policies — permanent standard time, permanent daylight saving time and biannual shifting — could affect people’s circadian rhythms, and, in turn, their health throughout the country. Circadian rhythm is the body’s innate, roughly 24-hour clock, which regulates many physiological processes.
The team found that, from a circadian perspective, we’ve made the worst choice. Either permanent standard time or permanent daylight saving time would be healthier than our seasonal waffling, with permanent standard time benefitting the most people.
Indeed, by modeling light exposure, circadian impacts and health characteristics county by county, the researchers estimate that permanent standard time would prevent some 300,000 cases of stroke per year and result in 2.6 million fewer people having obesity. Permanent daylight saving time would achieve about two-thirds of the same effect.
“We found that staying in standard time or staying in daylight saving time is definitely better than switching twice a year,” said Jamie Zeitzer, PhD, professor of psychiatry and behavioral sciences and senior author of the study to publish Sept. 15 in the Proceedings of the National Academy of Sciences. The lead author is Lara Weed, a graduate student in bioengineering... (MORE - details, no ads)
INTRO: Every spring, Americans dutifully adjust their clocks forward to daylight saving time, and every fall, back to standard time — but no one seems very happy about it. The biannual time shift is not only inconvenient, it’s also known to be acutely bad for our health. The collective loss of an hour of sleep on the second Sunday in March has been linked to more heart attacks and fatal traffic accidents in the ensuing days.
Now, a study by Stanford Medicine researchers finds there are longer-term hazards as well — and better alternatives.
The researchers compared how three different time policies — permanent standard time, permanent daylight saving time and biannual shifting — could affect people’s circadian rhythms, and, in turn, their health throughout the country. Circadian rhythm is the body’s innate, roughly 24-hour clock, which regulates many physiological processes.
The team found that, from a circadian perspective, we’ve made the worst choice. Either permanent standard time or permanent daylight saving time would be healthier than our seasonal waffling, with permanent standard time benefitting the most people.
Indeed, by modeling light exposure, circadian impacts and health characteristics county by county, the researchers estimate that permanent standard time would prevent some 300,000 cases of stroke per year and result in 2.6 million fewer people having obesity. Permanent daylight saving time would achieve about two-thirds of the same effect.
“We found that staying in standard time or staying in daylight saving time is definitely better than switching twice a year,” said Jamie Zeitzer, PhD, professor of psychiatry and behavioral sciences and senior author of the study to publish Sept. 15 in the Proceedings of the National Academy of Sciences. The lead author is Lara Weed, a graduate student in bioengineering... (MORE - details, no ads)