If I Could Turn Back Time: Daylight Savings Time and health

By Karen L. Kier
Pharmacist on behalf of the ONU Healthwise Team 

If I Could Turn Back Time was a 1989 song released by Cher. The video for the song was filmed on the USS Missouri naval battleship. As a performer, she has accomplished what no other female singer has done before. Cher has had a #1 hit in seven consecutive decades, with her first in 1965 with Sonny Bono.

Daylight Savings Time (DST) was first implemented in the United States with the Standard Time Act of 1918 to increase daylight to conserve energy during World War I.  This was instituted again with World War II.  After the war, local jurisdictions were able to choose whether to use DST or not until 1966.  In that year, The Uniform Time Act was passed for DST.  

There has been significant debate about DST at both the federal and state levels. Despite the debate, no real action has changed the current standard.  Does the impact on health change the debate?

In 2020, the American Academy of Sleep Medicine recommended the abolishment of DST in favor of a fixed national year-round standard time. The basis of this statement was evidence of health risks based on the impact of time changes on sleep patterns. Sleep is a critical component of a healthy lifestyle. The American Heart Association added sleep to its seven health lifestyle components to make “Life’s Essential 8.”

Your body is triggered by both light and dark as part of our daily circadian rhythm of waking up and going to sleep.  Our bodies' physically respond to light.  Recent studies have shown an increase in blood sugar when we are exposed to light while sleeping, which can increase the chance of developing diabetes.  

When we lose an hour in the spring, this results in less exposure to light in the morning with greater exposure to light in the evening. This change in light exposure disrupts sleep patterns both in waking in the morning and falling asleep at night.  

Published studies have documented sleep loss, more mood disturbances, increases in mental health issues, more emergency room visits and an increase in missed medical appointments with DST springing forward.  

A 2020 study in Current Biology analyzed 732,835 car accidents during the week following the spring forward DST change in time.  The researchers determined there was a six percent increase in fatal car accidents with the spring time change. The authors believe one hour of sleep deprivation is a leading factor.  

In the same scientific journal, a 2022 study researched the impact of fall DST in November on deer and motor vehicle accidents.  The researchers recorded a 16% increase in deer-related car accidents the week after the fall back time change. The authors indicated a 1.7% decrease in accidents if the U.S. stayed with a permanent DST.  

Besides accidents and sleep changes, some studies have suggested an impact on the heart and cardiovascular system by DST. A 2024 study in Mayo Clinic Proceedings published 5-year data evaluating cardiovascular (CV) health around both fall and spring DST, which contradicted older studies.  

The study evaluated 35,116,951 adults across the U.S. for heart issues 2 weeks before and 2 weeks after DST.  Individuals from the states of Arizona and Hawaii were excluded since they do not participate in DST. The spring DST showed a slight increase in CV events especially on the Monday and Friday after the time change.  The authors reported a slight decrease in CV events with the fall time change.  The researchers concluded that DST had no substantial impact on the heart.  

DST has some negative effects on health and sleep parameters as well as car accidents.  It might be time to end the debate and stop turning back time!

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