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Daylight Saving Time: A Case Study on the Impact of Sleep Loss

Have you ever wondered what would happen if you took millions of people and made them all get up an hour earlier than normal? Well, in many countries we do this every spring with the observance of Daylight Saving Time (DST). And the data researchers have gathered from this practice reveals a variety of health and safety implications, and serves as a powerful testament on the importance of making sleep a priority.

A Brief History of Daylight Saving Time in the USA
Daylight Saving Time began as a wartime measure to conserve the fuel used to light and heat buildings in World War I. It wasn’t particularly popular though, and was abolished until World War II, where it was renamed “War Time” and made mandatory. At the end of the war, it was left up to states to decide whether to continue the practice, or return to their old timekeeping measures.

It wasn’t until 1967 that the United States formally adopted Daylight Saving Time for the majority of the nation. States are allowed to “opt-out,” as Arizona and Hawaii have done, but only if the entire state chooses to do so.

More recently, in 2005 Congress voted to extend Daylight Saving Time by one month, bringing the “spring forward” from April to March, and the “fall back” from October to November, to allow for longer daylight during the summer.

Effect on Sleep
A recent survey of over 1000 adults showed that 61% say changing the clock affects their sleep, and 40% report that it takes them at least one full week to return to a normal sleep schedule, according to the Better Sleep Council.

The change in time can affect your sleep schedule by disrupting your routine. If shiftworkers work until 8am, for example, they may be getting home and getting into bed around 9am. When the clock shifts, their bodies still feel like it is 8am, and are gearing up for the commute home.

Effect on Performance and Workplace Fatigue
A 2009 study reported in the Journal of Applied Psychology reviewed data from the National Institute of Occupational Safety and Health tracking mining injuries over a period of 23 years. The researchers found that on Mondays directly following our “Spring Forward” switch to Daylight Saving Time, workers were more likely to sustain injuries – and even worse, sustain even more severe injuries than usual.

Along with the performance effects comes a natural effect on sleep for many shiftworkers. Researchers also examined Bureau of Labor Statistics data and found that following the switch to Daylight Saving, workers tend to sleep on average 40min less than usual.

Traffic Accidents

Be extra cautious while driving the first Monday of daylight saving time because traffic accidents are 8.6% more common. That’s according to an analysis of Canadian data that appeared in the New England Journal of Medicine in 1996. (

Heart Attacks

A 2012 report in the journal Sleep Medicine reports that heart attacks are more likely in the first week after DST. Looking at nationwide data on hospital admissions in Sweden, researchers found that the incidence of heart attacks was 3.9% higher than usual in the first week after daylight saving time. (

Take Home Message

Daylight Saving Time serves as a reminder of the importance of making sleep a priority for all shiftowrkers. 

Managers should view Daylight Saving Time as an opportunity to emphasize the importance of practicing good sleeping habits to their shiftworkers. They should also advise their employees to be alert for accidents, incidents or decreased alertness. If employees are having a hard time "waking up" from Daylight Saving Time, then it might be the perfect time for your organization to refocus energy on ensuring shiftworkers get the best day's sleep possible.

Additional Sources:,0,2861449.story
Barnes, CM and Wagner, DT. “Changing to Daylight Saving Time Cuts Into Sleep and Increases Workplace Injuries.” Journal of Applied Pyschology 2009. Vol. 94, No. 5, 1305–1317.

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