The good news: You’ll get a great extra hour of sleep. The bad: It will be dark as a pocket by late afternoon for the next few months in the United States
Daylight saving time ends at 2 a.m. local time on Sunday, which means you have to set your clock back an hour before going to bed. Standard time will continue until March 9 when we will move forward again with the return of daylight saving time.
The spring time change can be tougher on your body. Dark mornings and light evenings can disrupt your body’s internal clock, making it difficult to fall asleep on time for weeks or longer. Studies have found an uptick in heart attacks and strokes immediately after the time change in March.
“Undoing” should be easier. But it may take some time to adjust your sleep habits, not to mention the downsides of leaving work in the dark or trying to exercise while there is still enough light. Some people with seasonal affective disorder, a type of depression usually associated with shorter days and less sunlight in the fall and winter, may also suffer from it.
Some health groups, including the American Medical Association and the American Academy of Sleep Medicine, have said it’s time to ditch the time switches, and that sticking to standard time is better aligned with the sun and human biology.
Most countries do not observe daylight saving time. For those who do – mostly in Europe and North America – the date for changing the clocks varies.
This article is part of AP’s Be Well coverage, which focuses on health, fitness, diet and mental health. Read more Be well.
There are two states — Arizona and Hawaii — that do not change and adhere to standard time.
Here’s what to know about the twice-yearly ritual.
How does the body react to light?
The brain has a master clock that is set by exposure to sunlight and darkness. This circadian rhythm is an approximately 24-hour cycle that determines when we feel sleepy and when we are most alert. Patterns change with age, which is one reason young people who wake up early develop into teens who are difficult to wake up.
Morning light resets the rhythm. By evening, levels of a hormone called melatonin begin to rise, leading to drowsiness. Too much light in the evening — that extra hour of daylight saving time — delays this increase and the cycle gets out of sync.
This biological clock affects more than sleep, as it also affects things like heart rate, blood pressure, stress hormones, and metabolism.
How do time changes affect sleep?
Even changing the clock on the clock can throw off sleep schedules — because even though the hours change, the start times for work and school remain the same.
This is a problem because many people are already sleep deprived. About 1 in 3 U.S. adults sleep less than the recommended seven hours each night, and more than half of U.S. teens don’t get the recommended eight extra hours on weeknights.
Sleep deprivation is linked to heart disease, cognitive decline, obesity and many other problems.
How to prepare for the time change
Some people try to prepare for the time change by changing their sleep times little by little in the days leading up to the change. There are ways to make adaptation easier, including getting more sunlight to help reset your circadian rhythm for healthy sleep.
Is the United States getting rid of the change of time?
Lawmakers sometimes propose getting rid of the time change altogether. The most notable recent attempt, a bipartisan bill called the Sunshine Protection Act, proposes to make daylight saving time permanent. Health experts say lawmakers got it wrong — the standard time should be made permanent.
Dairy farmer Aubrey Jarrell in Kentwood, Louisiana, is not a fan of the time change. He said it interferes with his cows’ strict milking routine and causes them stress, “and stress on a dairy cow is not good.” He said there is a decline in milk production so they can adapt.
“Keep time the same — whatever it is — but keep it the same,” he said.
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