Spring Forward: The Science Behind the Time Change
Each spring, clocks move forward one hour as part of Daylight Saving Time, a practice designed to extend evening daylight. While the shift may seem small, research shows that losing even one hour of sleep can temporarily disrupt the body’s circadian rhythm, the internal biological clock that regulates sleep, hormones, and metabolism. When this rhythm is disturbed, the body may experience short-term stress as it adjusts to the new schedule. Scientists have found that this disruption can influence physiological processes such as blood pressure, heart rate, and sleep patterns.
Thomas Wolf (Der Wolf im Wald), CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons
Peer-reviewed studies suggest that the spring transition may also be associated with measurable health effects. A population-based analysis of medical records in the United States and Sweden found increased risks for several conditions—including cardiovascular disease, injuries, and immune-related illnesses—following daylight saving time shifts. Researchers estimated that the spring transition is linked to thousands of additional health events each year due to sleep disruption and circadian misalignment. Another study reported that heart attack rates increased significantly in the days following the spring time change, supporting the idea that even short periods of sleep loss can influence cardiovascular health.
Despite these findings, scientists continue to study the long-term impacts of daylight saving time, and some research suggests that the overall health effects may be small or vary among populations. Still, many experts agree that consistent sleep schedules and adequate sleep are important for maintaining healthy circadian rhythms. Understanding the biological effects of the “spring forward” time change highlights how closely human health is tied to sleep and natural light cycles.
Citations
Tanaka, S., & Koizumi, H. (2024). Springing Forward and Falling Back on Health: The Effects of Daylight Saving Time on Acute Myocardial Infarction. Journal of Economic Behavior and Organization.
https://www.cato.org/research-briefs-economic-policy/effect-daylight-saving-time-heart-attacks
Roenneberg, T., et al. (2020). Measurable health effects associated with the daylight saving time shift. Current Biology.
https://pubmed.ncbi.nlm.nih.gov/32511231/
Harvard Medical School sleep research summary on daylight saving health effects.
https://www.nationalgeographic.com/health/article/daylight-savings-heart-health