What are the health effects of Daylight Saving Time?

By K Ask daylight saving time, heart attack, sleep

Question: Every year I dread when March rolls around and I have to set my clock forward an hour. I wake up miserable and groggy for the entire week until I get used to the new time. I can’t imagine any of this is healthy. Does Daylight Saving Time have any negative effects on health? – Matt

Daylight Saving Time

We love getting an extra hour in fall but absolutely hate giving it back up when we “spring” forward. Daylight Saving Time (DST) is an old (some say outdated) concept which supposedly allows us to use daylight more efficiently. Our leaders enacted DST to reduce energy consumption. Whether or not it has outlived its usefulness is up for serious debate.

Giving up an hour of sleep might not be so serious if we actually got the recommended amount of sleep to begin with. Unfortunately, 40% of Americans get less than the recommended amount of sleep each night¹. Our perpetually sleep deprived state makes this week even harder to adjust to than a normal case of the Mondays. Research has shown there are plenty of negative effects of DST.

What does the research say about the health effects of Daylight Saving Time?

Study 1: Shifts to and from Daylight Saving Time and Incidence of Myocardial Infarction

The first article examined whether going into or out of DST affected the rates of acute myocardial infarctions (heart attacks). Researchers compared the number of heart attacks in the week after the time change (in both fall and spring) to the average number of heart attacks for the two week period prior to the time change².

The numbers showed a significant increase in the number of heart attacks following the start of DST (spring forward). In the fall, heart attacks after the time shift were below the preceding two week average².

Study 2: Changing to daylight saving time cuts into sleep and increases workplace injuries

The second article looked into multiple studies examining the relationship between losing one hour of sleep in the Spring and an increase in workplace accidents. Researchers found on the Monday following the loss of an hour, miners sustained more injuries of greater severity. They did not find any significant differences in the number or severity of injuries following the Monday after the gain of an hour of sleep (fall back)³.

Study 3: Adverse Effects of Daylight Saving Time on Adolescents’ Sleep and Vigilance

This study looked into the effects of starting DST on high school students’ vigilance and wakefulness during the school day. Researchers found students lost an average of 32 minutes of sleep on the weeknights following the start of DST. Students were given various tests to determine performance. Results showed a decrease in psychomotor vigilance testing performance, longer reaction time, and increased daytime sleepiness⁴.

Study 4: Transition to daylight saving time reduces sleep duration plus sleep efficiency of the deprived sleep

The final study looked at the effects of DST on sleep duration and efficiency. Researchers looked at the rest-activity cycles of 10 adults for 10 days during the transition into DST for 2003 and 2004. Researchers found participants lost an average of 60 minutes of sleep following the start of DST. Additionally, the subjects’ sleep efficiency decreased 10%⁵.

Daylight Saving Time and Health

The research is clear: in the short term, DST definitely affects both sleep quantity and quality. Most people will lose 30-60 minutes of sleep in the days following the Spring time shift. This decrease in sleep time and reduction in quality leads to other issues: increase in heart attacks, decreased vigilance on the job, increased injuries, and decreased performance.

The Bottom Line

Good sleep habits go a long way in improving sleep quality and mitigating the unintended consequences of DST. Before the time shift, try going to sleep and waking up earlier. Avoid alcohol, caffeine, and electronic device use before going to bed. Sufficient physical activity makes falling asleep easier. Unfortunately, there’s not much we can do to get rid of DST (write your elected officials). We can however, lessen the undesirable effects DST has on our performance and overall health.