It is just about time to “fall back” into daylight saving, rewinding time and setting the clocks back an hour to afford us one more precious hour of daylight in the morning.

Arguments for and against daylight saving time (DST) have persisted since it began in Europe during the First World War and spread to the rest of the world during the Second World War and the 1970s oil crisis. Proponents of the change argue that it saves energy, but how much tends to be marginal and varies between geographic regions. There are certainly some pros to DST: More light during the day leads to greater safety on the roads for both drivers and pedestrians, as well as a decrease in petty crime. At northern latitudes that see a much starker difference in daylight between the seasons, DST can save energy and requires less artificial light, which in turn can positively affect public health. Yet a growing body of evidence suggests that the negative effects of DST, paired with technological advances that make it obsolete, largely outweigh the benefits.  

So, how exactly do time changes impact human health?

DST Is Linked To Cardiovascular Health And Heart Attacks

Transitions in and out of DST can disrupt the “chronobiological rhythms” and influence the quality and duration of sleep, according to a 2008 study published in the New England Journal of Medicine. Researchers tracking the incidents of heart attacks in the two weeks before and after DST over the course of several years found a spike in reported heart attacks after the spring shift. However, this trend was reversed in the fall.

High School Students May Negatively Suffer From Lack Of Sleep

In a small study of just 35 high school students, scientists found that sleep declined by about 30 minutes on the weeknights in the days following DST, reflecting a total loss of 2 hours and 42 minutes. This lack of sleep saw declines in productivity and performance in school.

Loss Of Sleep During DST Linked With More Workplace Injuries

Losing just one hour of sleep from DST may pose dangerous consequences for employees in hazardous workplaces. Between 1983 and 2006, there were 3.6 more injuries on Mondays following the switch to DST reported to the US Mine Safety and Health Administration, contributing to a loss of more than 2,600 workdays, according to a 2009 study published in the Journal of Applied Psychology.

Depressive Episodes Increase During Autumn Transition

In an analysis of more than 185,000 hospital contacts, researchers writing in the journal Epidemiology found that the transition from summertime to standard time was associated with an increase in the rate of depressive episodes, largely sparked by the “sudden advancement of sunset” that marks the “coming of a long period of short days.”

Drivers Are More Likely To Be Involved In A Car Accident

A 2016 study published in the American Economic Journal found that sleepiness associated with DST contributed to more than 30 deaths out of more than 40,000 every year between 2002 and 2011. These deaths are largely driven by sleep deprivation and come at a social cost of about $275 million each year.

But Does It Really Make Us Sick?

In a comprehensive study of more than 3 million US respondents and 160 million German hospital admissions over a decade, Cornell researchers did “not find much evidence that population health significantly decreases when clocks are set forth by one hour in the spring.” However, this changed during the fall months when an increase of sleep by one hour saw public health “slightly” improve for about four days.

Due to concerns over health and wellness, several governments across the globe have set forth initiatives to end the practice. Last year, an international survey of EU citizens largely supported the notion of nixing the bi-annual ritual and some US states and territories have foregone the notion entirely. As it stands, many countries around the world switch their times on different days, and some do not practice DST at all. Time and Date has compiled a complete list of when and where around the world we’ll be seeing clocks set back.