Overview
- Researchers estimate that adopting permanent standard time could prevent about 300,000 strokes each year and reduce obesity by roughly 2.6 million people in the United States.
- Permanent daylight saving time also shows health benefits but at about two-thirds the magnitude, with an estimated 220,000 fewer strokes and 1.7 million fewer people with obesity.
- The study identifies the twice-yearly clock change as the least healthy option for circadian rhythms compared with either permanent policy.
- The analysis models county-level light exposure from sunrise and sunset to quantify circadian burden and links it to CDC disease prevalence, with findings published in PNAS and supported by NIH funding.
- Authors caution that the estimates assume circadian-friendly light habits and do not fully capture weather or behavior, as medical groups back year-round standard time and federal legislation remains unresolved.