Intended for healthcare professionals

Feature Daylight saving time

Why health experts are fighting to end daylight saving time

BMJ 2023; 380 doi: (Published 23 March 2023) Cite this as: BMJ 2023;380:p622
  1. Chris Baraniuk, freelance journalist
  1. Belfast
  1. chrisbaraniuk{at}

As evidence for the health hazards of twice yearly time switching grows, countries still using daylight saving time must decide which of two time systems is preferable. Chris Baraniuk reports

There’s a showdown brewing in Tennessee. Beth Ann Malow, professor of neurology at Vanderbilt University Medical Center, is one of many health experts campaigning for an end to daylight saving time. She wants her state, and six neighbouring southern states, to secede on this matter together and enshrine permanent standard time into law.

“Once they agree to go to standard time as a region we wouldn’t need the federal government to tell us what to do,” she explains. Among the neighbouring states she hopes would join such a movement are Alabama, Arkansas, and Mississippi. If all seven states moved together, people travelling around this region wouldn’t have to adjust to different times, she adds.

Malow and other health experts argue that permanent standard time increases people’s exposure to morning sunlight, which is associated with improved sleep.1

A string of studies published in recent years suggests that a twice yearly time shift is bad for us for lots of reasons. The loss of one hour of sleep in spring, in particular, has been linked to an increase in heart attacks, strokes, road accidents, and negative mood.

Modern daylight saving time was first introduced in two Canadian towns in 1908, to allow residents to gain an hour of sunlight in the evening. The idea soon spread around the world, largely through colonial empires. It has, however, since vanished from many of the territories on which it was imposed during the twentieth century.

Although daylight saving remains common in Europe and North America, most countries in Africa, Asia, and Latin America do not observe seasonal clock changes. And some nations have recently …

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