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  • Writer's pictureAlan Frischer, MD, MPH

Daylight Savings Time

We recently moved our clocks forward one hour, essentially shifting an hour of daylight from the morning to the evening, and starting daylight savings time up again. The good news is that this gives us those long summer evenings. However, we won’t see that hour again until the fall. What impact does that have on our health?

Light is the cue that sets and resets our 24-hour internal clock, known as circadian rhythm. Moving our clocks in either direction changes this, and our biological clock falls out of sync. In general, losing an hour as we just did is more difficult than is gaining an hour in the fall. Think about airplane travel: in general, our bodies find it easier to travel west, where we gain time, than to travel east.

Daylight savings time transitions often lead to disrupted sleep cycles. Springing forward requires that we go to sleep earlier. On average, for the first few days of setting the clocks forward in the spring, we lose 40 minutes of sleep. Even this relatively small sleep loss has been shown to have consequences.

Many experience an increase in mood disturbances, and increased irritability. Studies show that people who are sleep deprived develop a more sensitive amygdala, the emotional center of the brain. It becomes more reactive to disturbing images as compared to those who are more rested.

Loss of sleep can cause a decrease in motor skills, which leads to more workplace injuries. One study revealed a 5.7% increase in workplace injuries on the Monday following the time change. The injuries were more severe, leading to a 68% increase in the number of days of work missed. Research also reveals a 6% increase in car accidents immediately after we reset our clocks in the spring.

Other studies show an 8% higher rate of ischemic stroke in the first two days following both the spring forward and fall behind time changes. A 2014 study found a 25% jump in the number of heart attacks on the Monday after daylight savings time begins. Interestingly, the opposite occurred, with a 21% drop in the number of heart attacks following the end of daylight savings in the fall.

Sleep deficiencies also can cause an increase in the release of the hormone ghrelin, which leads to hunger, and a decrease in the release of the hormone leptin, which makes us feel satisfied when we eat. These changes in hormone levels can wreak havoc on our diet and weight control.

Have you heard the term cyberloafing? Workers spend significantly more time searching for entertainment content (YouTube and other videos, and music) specifically on the Monday following a time change.

Who might be affected the most? Those who are already sleep-deprived, or consume alcohol or caffeine close to bedtime. Keep these tips in mind for dealing with future time changes:

  • Give yourself a jump-start to adjusting to a time change. Try going to bed and waking up a bit earlier, or later, than usual, before the change occurs.

  • Light is the principal environmental cue. Expose yourself to sunlight as soon as you wake up and during waking hours. Seeing light first thing in the morning can help reset your body’s clock. Try eating breakfast in front of a window or taking an early morning walk. On the other hand, avoid exposure to bright artificial light when it is dark outside and close to your bedtime.

  • Make your environment sleep-friendly, and practice good “sleep hygiene.” This includes avoiding caffeine, alcohol, or other stimulants after lunch. Don’t exercise immediately before bedtime, and create a calming bedtime ritual. Go to bed and rise around the same time each day.

  • Avoid daytime naps, which decrease your ability to sleep at night.

Give yourself an extra break when there is a time change. Avoid driving if you are sleep deprived. Take care of yourself and listen to what your body is trying to tell you, and you will be ready for November 4th - when we’ll finally get our hour back!

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