Is Daylight Saving Time Bad for Your Health??>

Is Daylight Saving Time Bad for Your Health?

by David Wild

Losing an hour of sleep on the second Sunday in March is a simple annoyance for most, but some studies have linked serious health consequences to the shift to daylight saving time (DST). Below are some examples of how springing forward might set our health back.

Sleep loss

Much of the blame for DST’s health effects stems from sleep loss. That lost hour can interfere with the body’s circadian rhythm—our natural sleep/wake cycle. According to one 2013 study, it takes about a week for our bodies to adapt to a time change, which can result in problems like falling and staying asleep and waking up, leaving us sluggish and sleep deprived.

Heart attacks

Some data suggests that the risk of heart attacks increases when we turn the clocks forward. Research published in the March 2019 issue of the Journal of Clinical Medicine analyzed seven studies of more than 115,000 patients who had heart attacks in the weeks shortly after DST or in the weeks following the return to standard time in the fall. Overall, the analysis showed a higher incidence of heart attacks during the two weeks after DST, but no significant difference in the rates of heart attack after the fall switch back to standard time.

One study in the analysis reviewed more than 25,000 heart attack cases and found that, overall, heart attacks were no more common during time changes than at any other time of year. However, researchers did find that a subset of persons who had a prior heart attack as well as people taking angiotensin (ACE) inhibitors—a common blood pressure and heart failure treatment—may have a higher risk of a heart attack in the week after the spring shift than similar patients not taking the drug.

Studies like those in the analysis, however, have limitations, like their reliance on data from registries, insurance databases, and hospital discharge notes. Such sources can exclude relevant information that could better explain the outcomes.


The strongest case for a risk of stroke with DST comes from a Finnish registry-based study published in Sleep Medicine in 2016 that found a higher risk of ischemic stroke–related hospitalizations during the first two days after a DST switch. The risk was particularly high among women and adults older than 65. Stroke incidence may be connected to circadian rhythm changes, say the researchers. They also point to other studies that tie stroke risk to either too little or too much sleep.

Traffic accidents

Whether DST directly leads to more car accidents is not clear, as study results have been mixed. A study that investigated traffic accidents in the United States from 1975 to 1995 found an increase in fatalities on the Monday after DST and the Sunday after the return to standard time. The researchers attributed the rise to driver sleepiness and the disruption of sleep timing, respectively. Then again, a 2010 study found no effect on traffic accidents in Minnesota over six years during either spring or fall transitions. And, a 25-year traffic study in Finland saw no differences in accident rates during the week before and after the time changes.

Why We ‘Spring Forward’ (and ‘Fall Back’)

The idea of changing the local time so that peak periods of activity coincide with daylight is widely attributed to Benjamin Franklin, who first suggested it in 1784. But it wasn’t permanently adopted in the United States until 1966.

How to adapt

It’s important to realize that the data on DST and health implications aren’t ironclad. Additionally, because the studies are all observational, they can’t prove that DST is a direct cause of the health consequences; they can show only an association between the two. Still, if you tend to struggle to adapt to the spring time change, try these strategies to help manage the lost hour of sleep:

  • Go to bed 15 to 20 minutes earlier than usual in the days leading up to the time change, or at least on the night of the time change.
  • Sleep in for an extra half hour on the Sunday morning after the clocks change.
  • Get some sunlight early in the morning on the days after the switch. If that’s challenging, consider using a lightbox or a dawn simulator.
  • Start adjusting the timing of daily routines that are “time cues” for your body, like eating dinner earlier in the nights leading up to the spring switch to DST.
  • In the early evening before the DST switch, set your clock ahead one hour and go to sleep at your usual hour, according to the new time.
  • Make sure to go to bed at your usual hour on Sunday night to get enough sleep before the workweek starts.

This article first appeared in the April 2020 issue of UC Berkeley Health After 50.

Also see Chronotherapy: Timing Your Medications.