Five Negative Effects of Daylight Savings Time

As daylight saving time ends at 2 a.m. this coming Sunday morning, most Americans will join snoozers across more than 60 other nations in savoring the gift of one extra hour of sleep. Though the biannual ritual of turning clocks might feel like second nature to us today, it is actually a fairly new phenomenon that has only taken effect on a global scale within the past several decades. In this article, we explore five strange ways that daylight saving time, and the ending of it, affect human health.

More Car Accidents

One effect of daylight saving time is an increase in car accidents. The general concept supporting the case is that subtle changes in sleep patterns and circadian rhythms can alter human alertness and, in some cases, might increase the risk of potentially fatal car accidents. However, studies have had mixed results. One study found no significant change in the number of accidents during this time period, while another found that daylight saving time can actually result in fewer crashes by increasing visibility for drivers in the morning.

Increased Workplace Injuries

Another effect of daylight saving time is an increase in workplace injuries for certain types of workers, such as miners. Workers have been shown to experience more frequent and severe workplace injuries at the onset of daylight saving time in the spring. Lack of sleep is attributed to the injuries, which might explain why the same effect did not pop up in the fall when workers gained an hour of sleep.

More Heart Attacks

A study conducted in Sweden showed the rate of heart attacks during the first three weekdays following springtime daylight saving time increased by about 5 percent from the average rate during other times of the year. The researchers attributed the small surge in heart attacks in the springtime to changes in people's sleep patterns. Lack of sleep can release stress hormones that increase inflammation, which can cause more severe complications in people already at risk of having a heart attack.

Longer Cyberloafing

The incidence of cyberloafing significantly increased in more than 200 metropolitan U.S. regions during the first Monday after daylight saving time in the spring, compared with the Mondays directly before and one week after the transition. The team attributed the shift to a lack of sleep and thus lack of workday motivation and focus.

Increased Cluster Headaches

Circadian rhythms tick away throughout the body each day, controlling the release of certain hormones that affect moods, hunger levels, and yearning for sleep. When these rhythms get thrown out of whack, even by just one hour during daylight saving time, the human body notices the difference. For some people, the effects of this change can set off debilitating chronic pain, such as cluster headaches.

In conclusion, daylight saving time can have some unusual and unexpected effects on the human body. From increasing the risk of car accidents to causing cluster headaches, the subtle time shift can take a noticeable toll on human health. While it might be tempting to hit the snooze button for that extra hour of sleep, it's worth being aware of the potential effects of the time change and taking steps to mitigate them.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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