The body’s circadian rhythms vary due to different levels of sunlight exposure. The key lies in the morning light.
Ending the twice-yearly ritual of changing clocks could prevent 300,000 strokes and 2.6 million cases of obesity annually across the United States, according to new research from Stanford Medicine.
The study, published in the Proceedings of the National Academy of Sciences, compared three time policies and found that maintaining permanent standard time—essentially staying on “winter time” year-round—offers the greatest health benefits.
“Staying in standard time or staying in daylight saving time is definitely better than switching twice a year,” senior study author Jamie Zeitzer, professor of psychiatry and behavioral sciences at Stanford University, said in a statement.
Not Changing Time Is Healthier
The team found that, from a biological perspective, adhering to either standard time or daylight saving time year-round would be better for health than switching twice a year, with permanent standard time offering the most benefit.
The research team used mathematical models to analyze how different time policies—such as daylight saving, standard time, or changing time scheduling—affect the body’s circadian rhythm due to varying sunlight exposures.
Researchers then predicted health outcomes based on these different time conventions after taking into account current obesity and stroke rates.
Their findings suggest that maintaining a permanent standard time could lower obesity prevalence by 0.78 percent and stroke rates by 0.09 percent—translating to 2.6 million fewer obesity cases and 300,000 fewer strokes nationwide. Permanent daylight saving time would achieve roughly two-thirds of those benefits.
“Light triggers certain brain regions to prepare us for the day’s challenges,” Dr. Stephen Carstensen of Seattle Sleep, who was not involved in the study, told The Epoch Times.
Zeitzer said in the statement that the human circadian cycle naturally runs slightly longer than 24 hours.
When you get light in the morning, it speeds up the circadian cycle to promote wakefulness, and the darkness at night stimulates melatonin, which prepares you for sleep.
Most people would benefit from staying on standard time, as it is aligned with the sun, allowing them more light in the mornings. Daylight saving time, on the other hand, is one hour ahead, and therefore makes people out of sync with the sun.
