Daylight saving time starts Sunday at 2 a.m., which means we get another hour of natural light at the end of the day — and lose an hour of sleep we won't get back until November.
Most people can easily adapt to the change — provided they remember to turn their clocks ahead before bed. But others have a harder time.
"We are essentially forcing our bodies to advance their internal biological rhythm," said Karl Doghramji, medical director of the Jefferson Sleep Disorders Center at Thomas Jefferson University Hospital.
An hour might not sound like much, but many of us don't sleep enough to start with.
About 40 percent of American adults do not get the recommended seven hours of sleep a night, according to the U.S. Centers for Disease Control and Prevention.
Adults who had less than seven hours of sleep in a 24-hour period were more likely to report problems with 10 chronic health conditions, including heart disease, diabetes, obesity, asthma, and depression, compared with those who slept seven or more hours, according to Michael S. Jaffee, a neurologist at the University of Florida.
There is also a small increase in fatal accidents on the Monday after the shift to daylight saving time, according to a Stanford University study, which analyzed 21 years of accident data. The impact is also seen after the autumn time change, when drivers may use the extra hour to stay out later. Researchers believe that increase can be attributed to more drunken drivers on the road.
A University of Pennsylvania study found that the end of daylight saving each fall is linked to a short-term increase in the assault rate.
Seniors and people on certain medications have more difficulty making the change, Doghramji said.
And so do children and teens. Kids ages 6 to 12 years should get nine to 12 hours of sleep a day. Teens 13 to 18 years should sleep eight to 10 hours daily, according to the American Academy of Sleep Medicine. A full night's sleep improves attention, helps with memory, behavior, learning, and improves quality of life.
Teens, if you can persuade them, should try to wake up a few minutes earlier in the days leading up to the change, Doghramji suggested.
"Chances are they are not going to do it," he said. And if you insist on an early bedtime, that doesn't mean they'll be able to fall asleep, he noted.
But it's not their fault — teens are biologically programmed to go to bed later and sleep later. No less an authority than the American Academy of Pediatrics has urged that middle schools and high schools start no earlier than 8:30 a.m., a plea that hasn't been heeded in many places.
"All of us will lose an hour, but for teens, their circadian rhythm changes at puberty, so the earliest they can fall asleep is later than 11 p.m.," Norr said. "They can't help it. It's biology."
Monday morning after the time change will be particularly tough on teens, Norr said.
If you are having trouble adjusting to the time change, the National Sleep Foundation recommends you go to sleep and wake up at the same time every day, avoid bright lights in the evening, and get some sunshine in the morning. Only use the bedroom for sleeping and sex, not for work or television-watching. Consider adopting a bedtime ritual like a warm bath. Regular exercise will also help sleep patterns.