[00:00.00]Much of the United States "springs forward" on Sunday, March 9th, for daylight saving time.
[00:09.69]Worldwide, many other countries also observe daylight saving time, starting and ending on different dates.
[00:21.80]The time change can leave people tired and perhaps unhappy the next day.
[00:30.58]But it also might even harm health.
[00:35.65]Some studies have found an increase in heart attacks and strokes right after the March time change.
[00:46.10]However, there are ways to ease the effects of the time change, including getting more sunshine.
[00:56.76]The light helps reset your circadian rhythm for healthful sleep.
[01:04.62]In the U.S., daylight saving time begins Sunday at 2:00 in the morning.
[01:13.24]The time change will reverse on November 2 when clocks "fall back" as daylight saving time ends.
[01:25.78]The state of Hawaii and most of the state of Arizona do not make the spring change.
[01:34.26]Those areas remain on standard time along with Puerto Rico, American Samoa, Guam and the U.S. Virgin Islands.
[01:48.47]Some people try to prepare for the change to daylight saving time by going to bed a little earlier two or three nights ahead.
[02:01.67]But with a third of American adults already not getting the suggested seven hours of nightly sleep, catching up can be difficult.
[02:15.92]The brain has a kind of clock that is set by exposure to sunlight and darkness.
[02:25.48]This clock, known as the circadian rhythm, is on a roughly 24-hour cycle.
[02:35.08]It governs when we become sleepy and when we are more wakeful.
[02:41.57]The rhythms change with age.
[02:45.94]This is one reason that early-to-rise young children turn into hard-to-wake teenagers.
[02:57.21]Morning light resets the rhythm.
[03:00.80]By evening, levels of a hormone called melatonin begin to increase, leading to tiredness.
[03:10.93]Too much light in the evening - that extra hour from daylight saving time - delays the melatonin increase.
[03:22.05]As a result, the cycle gets delayed.
[03:26.34]The circadian rhythm affects more than sleep.
[03:31.48]It also influences heart rate, blood pressure, hormone releases and other systems.
[03:40.62]Sleep deprivation, or lack of sleep, is linked to heart disease, weight conditions, problems with thinking and remembering, and more.
[03:55.03]Deadly car crash numbers increase the first few days after the spring time change, a study of U.S. traffic deaths says.
[04:07.18]The risk of crashes is highest in the morning, it found.
[04:12.73]Researchers suggested sleep deprivation might be responsible.
[04:19.63]The time change also has a link to the heart.
[04:24.87]The American Heart Association points to studies that suggest an increase in heart attacks on the Monday after daylight saving time begins, and in strokes for two days afterward.
[04:42.98]Doctors already know that heart attacks, especially severe ones, are a bit more common on Mondays generally - and in the morning, when blood is more likely to clot.
[04:59.82]Researchers do not know why the time change would add to that Monday connection.
[05:07.57]But it is possible the sudden circadian change influences other issues such as high blood pressure in people already at risk.
[05:20.98]To prepare for daylight saving time, experts offer some advice.
[05:28.35]Slowly move bedtimes about 15 or 20 minutes earlier for several nights before the time change.
[05:39.36]Try to rise earlier the next morning, too.
[05:45.09]Go outside for early morning sunshine the first week of daylight saving time.
[05:53.10]This is another way to help reset your body's clock.
[05:59.51]Start daily activities, like dinner or exercise, a little earlier.
[06:07.60]This may help tell your body to start getting used to the new conditions, sleep experts suggest.
[06:16.99]Daytime sleeping, the drug caffeine and light from phones and other electronic devices can make an earlier bedtime even harder.
[06:31.53]Americans have discussed ending daylight saving time.
[06:37.37]But so far, no official changes have been made.
[06:42.96]Health groups such as the American Medical Association and American Academy of Sleep Medicine believe it is time to end time changes.
[06:56.90]The groups suggest that staying with standard time year-round works better for human biology and sleep needs.
[07:09.22]I'm Caty Weaver.
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Words in This Story
circadian rhythm - n. the mental, behavioral, and physical changes a person experiences over a 24-hour period
exposure - n. the condition of being subject to some effect or influence
reverse - v. to undo, to turn about in position or direction
cycle - n. a series of events that take place regularly and return to the same starting point
hormone - n. a product of living cells that circulates in the body and produces an effect on the activity of cells
clot - v. to undergo chemical reactions that result in blood becoming a lump or mass (a clot)
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