How daylight saving time affects your sleep and overall health

Ashley May


Published 5: 01 AM EDT Nov 1, 2019

Daylight saving time ends and clocks will “fall back” an hour this weekend, giving Americans the feeling of an extra hour in the morning, which could negatively affect their health. 

“Ever since the institution of daylight saving time, there has been controversy regarding whether it accomplishes its goals or not, and if so – at what cost,” Timothy Morgenthaler, Mayo Clinic’s co-director of the Center for Sleep Medicine, said in a 2018 interview.

Morgenthaler has reviewed about 100 medical papers related to how the time change could affect health.

Here’s what you should know:


Gaining or losing an hour will likely affect sleep patterns, often for about five to seven days, Morgenthaler said. The most notable changes are in those who regularly do not get enough sleep. People who are sleep deprived might struggle with memory, learning, social interactions and overall cognitive performance.

“People have more changes in how sleepy they feel or how it affects the quality of their sleep when we ‘spring forward’ than when we ‘fall back,'” Morgenthaler said.

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Heart attack or stroke

According to a study led by a University of Colorado fellow in 2014, when Americans lose one hour of sleep in the spring, the risk of heart attack increases by 25%. When the clock gives back that hour of sleep the risk of heart attack decreases by 21%. (The limited study looked at hospital admission data in Michigan over a four-year period.)

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A preliminary study presented at the 2016 American Academy of Neurology meeting suggested turning the clock ahead or behind an hour could increase the risk of stroke. That’s because disrupting a person’s internal body clock might increase the risk of ischemic stroke, the most common type of stroke, according to researchers. The data showed the risk of ischemic stroke was 8% higher two days after a daylight saving time. 

These studies are two of several on these negative health effects, and they don’t always paint the whole picture, Morgenthaler said. 

“Of several published between 2010 and 2014, three studies showed that DST increases the risk of acute myocardial infarctions (AMIs), however, two others demonstrated that the timing (but not the incidence) of strokes and AMIs may be influenced by DST,” Morgenthaler points out. 

Car crashes

Many have also studied the time change’s impact on vehicle crashes and fatalities. The largest studies that correct for volume and driving activity as well as the time of day “show no significant effect” on daylight saving time changes, Morgenthaler said. Still, he cautions to remain aware while driving or walking near a road, especially early in the morning or late at night, after the change. 

Editor’s Note: This article was originally published in 2018. 

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