Research Shows Permanent Standard Time Could Improve Americans' Health

Every year, Americans adjust their clocks twice—a shift in spring to daylight saving time and a return to standard time in fall. While necessary for many, this biannual change is inconvenient and has notable health impacts. The transition in spring, which results in losing an hour of sleep, has been associated with increased heart attacks and traffic accidents in the following days.

Recent research from Stanford Medicine offers a broader perspective, highlighting potential long-term health benefits of adopting a permanent time policy. The study compared three configurations: permanent standard time, permanent daylight saving time, and the current seasonal shifting. It focused on circadian rhythms—the body's internal 24-hour clock that regulates vital physiological processes.

The findings suggest that maintaining a single time system year-round—either standard or daylight saving—would be healthier for most people. According to models, permanent standard time could prevent approximately 300,000 strokes annually and reduce obesity cases by 2.6 million. While permanent daylight saving time also presents benefits, it is less effective overall.

Lead researcher Jamie Zeitzer, Ph.D., emphasized that both permanent standard and daylight saving time outperform the current seasonal shifting in terms of health impact. The study also delved into how light exposure affects circadian regulation. Morning light tends to speed up the internal clock, aligning it with natural day cycles, while evening light can delay it, leading to circadian misalignment.

Using mathematical modeling, researchers analyzed how different time policies influence light exposure and circadian health across regions. Most individuals would experience the least circadian stress under permanent standard time due to increased morning light exposure. Interestingly, early risers—about 15% of the population—might benefit more from permanent daylight saving time, which provides extra evening light.

The study further connected circadian alignment with health conditions, showing that permanent standard time could slightly lower instances of obesity and stroke across the U.S. However, the authors caution that real-life light exposure varies based on geography, weather, and individual habits, which the models do not fully account for.

While this research offers compelling evidence, it is just one piece of a complex discussion involving health, societal, and economic factors. Currently, legislation discussions continue about whether to adopt permanent standard time, permanent daylight saving, or stick with seasonal changes. Ultimately, aligning policies with scientific evidence could lead to healthier populations.

Source: https://medicalxpress.com/news/2025-09-americans-healthier-permanent-standard.html