Daylight Saving Time and Your Health: What Research Shows

Losing an hour overnight during the spring transition measurably shortens sleep for a large share of the population for several days afterward, since the body's circadian rhythm doesn't instantly reset to match the new clock.

Multiple studies have found a small but statistically detectable increase in traffic accidents and workplace injuries in the days immediately following the spring transition, generally attributed to accumulated sleep debt and reduced alertness.

The fall transition, which adds an hour rather than removing one, has not shown the same consistent negative pattern in research — consistent with it being the easier of the two changes to adjust to.

Because the effect is temporary — most measures return to baseline within roughly a week — gradually shifting sleep and light exposure in the days before the spring change is the most commonly recommended way to reduce its impact.

The consistent finding that spring's transition carries more measurable downside than autumn's has fueled ongoing debate in Congress over eliminating the twice-yearly switch entirely, including proposals such as the Sunshine Protection Act to make daylight saving time permanent — legislation that, as of 2026, has been introduced but not signed into law.

Sleep researchers have generally been more supportive of making standard time permanent instead, arguing that standard time keeps clock time better aligned with the body's natural light-dark cycle year-round, though that view has not driven federal policy so far.

Until any such legislation changes the underlying schedule, the practical guidance for individuals remains the same regardless of which side of the policy debate they favor: treat the spring transition as the one worth actively preparing for, and expect the fall transition to require little adjustment at all.