Daylight saving time has a dark side

By David Wagner

Losing sleep can be deadly. A train hurls around a corner at 82 mph, eventually coming off the rails and killing four passengers. Faulty decision-making results in the deaths of the seven-person crew of the Space Shuttle Challenger. A stuck valve regulating the supply of coolant to a nuclear reactor nearly results in the meltdown of a nuclear plant in Pennsylvania.

In each of these cases, poor or inadequate sleep was one of the factors that contributed to the failure.

More than a third of American adults sleep less than the suggested minimum seven hours a night, and two-thirds of American teens sleep less than their minimum recommended eight hours. Even for those with good sleep hygiene, there is one time of year when you are likely to be short on sleep – the annual shift to daylight saving time.

The American public has had a love-hate relationship with daylight saving time since it first became law in 1918. Personal preferences aside, the empirical evidence for the intended benefits are mixed at best, whereas the costs of the switch between time schemes are becoming increasingly evident.

At the crux of these costs is the effect of the time shift on our sleep patterns. When we spring forward, the clocks on the wall advance, but our body clocks do not change so readily. It generally takes a few days for us to adapt to the time change in a way that allows us to fall asleep at our typical time. The upshot is that Americans sleep approximately 40 minutes less than usual on the Sunday to Monday night following the switch.

A database of mining injuries from the National Institute of Occupational Safety and Health indicates that the spring shift to daylight saving time resulted in a 6 percent increase in mining injuries and a 67 percent increase in workdays lost because of these injuries.

White-collar workers feel the effects, too. By examining internet search patterns over six years in more than 200 American metro areas, we found that searches for entertainment or related categories were much more prevalent (3.1-6.4 percent) on the Monday immediately following the time change than they were on other Mondays. Given that much of this search activity was conducted at work, we concluded that workers are cyberloafing when they should be working. Such loafing on the job following the time change suggests that people are less productive when mildly sleep deprived due to the time change.

Economists estimate that the annual spring time change costs the American economy $434 million each year. Yet that is not where the costs end.

The shift to daylight saving time may influence our ability to perceive the moral features of a given situation. We again examined internet search behavior and followed up with our own experiment. In the experiment we kept half of our research participants awake throughout the night and allowed the other half to get a full night of sleep. The next day we presented them with scenarios that contained varying levels of moral content.

We found that the day following the shift to daylight saving time, or following a night of sleep deprivation, people were less able to discern when a situation involved issues of moral relevance than when they were well rested.

The time change also affects our judgment in formal settings. A recent study found that judges hand out harsher sentences — 5 percent longer in duration — the Monday following the time change, as compared with other days of the year. This means that sleep and public policy related to sleep could be influencing important decisions that should be impartial.

These studies are only the tip of the iceberg, with consequence of the time change ranging from student test scores to stock market returns.

Accumulating evidence suggests that the costs of shifting to daylight saving time cut across society. Many state legislatures have begun reconsidering the time change. Other states could end up joining Arizona and Hawaii in abstaining from daylight saving time.

As we move toward that possibility, it may become easier to save lives and money rather than chase the daylight.

David Wagner is an Associate Professor of Management at the University of Oregon. This article is republished from The Conversation under a Creative Commons license.

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