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Daylight Saving Time “fall back” doesn’t equal sleep gain

Posted By Anthony Komaroff, M.D. On November 1, 2013

Daylight Saving Time officially ends at 2:00 am this Sunday. In theory, “falling back” means an extra hour of sleep this weekend.

Winston Churchill once described Daylight Saving Time like this: “An extra yawn one morning in the springtime, an extra snooze one night in the autumn… We borrow an hour one night in April; we pay it back with golden interest five months later.”

That’s an overly optimistic view. In reality, many people don’t, or can’t, take advantage of this weekend’s extra hour of sleep. And the resulting shift in the body’s daily sleep-wake cycle can disrupt sleep for several days.

Research teams around the world have tried to determine if losing or gaining an hour of sleep because of Daylight Saving Time make a difference in health. This spring, Michigan researchers, writing in the American Journal of Cardiology, showed a small increase in heart attacks on the first day (Sunday) of the spring transition to Daylight Saving Time, when we “lose” an hour of sleep. This echoed a Swedish study published in the New England Journal of Medicine showing a small increase in heart attacks after the start of Daylight Saving Time and a small decrease at its end.

Other researchers have looked at driving accidents, workplace safety, and even school performance, with mixed results.

Daylight Saving Time and sleep

The focus on gaining or losing an hour of sleep overlooks the bigger picture—the effect of Daylight Saving Time transitions on the sleep cycle. An excellent review in the journal Sleep Medicine Reviews by Dr. Yvonne Harrison, a senior lecturer at Liverpool John Moores University in England, concludes that a seemingly small one-hour shift in the sleep cycle can affect sleep for up to a week.

In the Fall, only a minority of people actually get that promised extra hour of sleep. During the following week, many people wake up earlier, have more trouble falling asleep, and are more likely to wake up during the night. People who tend to be so-called short sleepers, logging under 7.5 hours a night, and early risers (also known as larks), have the most trouble adjusting to the new schedule.

Similar problems are seen in the Spring. Again, the adjustment is harder for larks and short sleepers.

Springing back

Each of us experiences predictable physical, mental, and behavioral changes during the course of a day. These are called circadian rhythms. The daily cycle of light and dark keep them on a 24-hour cycle.

Sleep is a component of circadian rhythms. It is affected by outside influences, like light or Daylight Saving time. It can also affect the body’s other rhythms.

It’s difficult to side-step the effects of Daylight Saving time on sleep. My advice is to be aware that it can take your circadian and sleep rhythms a week or so to get adjusted to the new clock. Regular exercise, preferably at the same time each day, may help get your sleep cycle back on track. Going to bed and getting up on a schedule can help. And giving in to brief afternoon nap or two during the week may be a pleasant and relaxing way to restore lost sleep.

Related Information: Improving Sleep: A guide to a good night’s rest

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