Changing the clocks is linked to a wide range of health effects from heart attacks to traffic accidents.
As the nights grow longer and we prepare to turn the clocks back, we often comfort ourselves with the thought of that extra hour of sleep the chance to stay under the covers a little longer. After all, a whole extra hour in the evening sounds great you could get so much more done!
But studies show it might not be quite as positive as it seems. Some research suggests a link between the autumn clock change and an increased risk of depressive episodes. On the bright side, turning the clock back in the fall appears to be less harmful to health than the spring shift forward, which has been associated with a higher risk of heart attacks, strokes, and traffic accidents.
A quick look back: Daylight Saving Time (DST) was first introduced in the United Kingdom in 1916, during World War I - as a measure to save energy and make better use of daylight during working hours. Since then, the clocks have been moved forward one hour on the last Sunday in March and back one hour on the last Sunday in October.
And it's not just a British phenomenon: around 70 countries and more than a quarter of the world's population observe Daylight Saving Time. In the United States, it was officially adopted in 1966. Today, Americans set their clocks forward on the second Sunday in March and back on the first Sunday in November. Increasingly, research suggests that these clock changes can have a negative impact on people's health. The strongest evidence points to the springtime shift forward, which makes mornings darker and evenings lighter and robs people of an hour of sleep.
"When you apply even a small risk to 60 million people, it adds up to a considerable number of entirely preventable health problems", explains David Ray.
In 2014, researchers in the U.S. found that the number of people admitted to hospitals on the Monday after the clock change rose by 24 percent. Similar findings have been reported in studies from Sweden, Croatia, Germany, Brazil, Finland, and Mexico. A meta-analysis combining all available studies found that the average number of heart attacks increases by about 4 percent after the start of Daylight Saving Time in spring a small but significant rise.
But that's not all. Further studies showed that the number of strokes increases in the weeks following the spring clock change. And while one might assume that more evening light could be beneficial for mental health, even that has been called into question: a 2020 study found that switching to Daylight Saving Time can worsen mood disorders, depression, anxiety, and substance abuse.
Finally, there's the issue of traffic accidents. In the U.S., it has been shown that the number of fatal car crashes rises in the weeks after the springtime shift. One study estimated that moving the clock forward increases the risk of deadly road accidents by 6 percent apparently because many people struggle with the loss of that one hour of sleep.
