Americans are night owls at age 20, get the least sleep at 40, and then finally get more shut-eye after retirement.
Those are among the key takeaways from a study that looked at the sleep patterns of Americans of all ages. In short, teenagers and young adults often fall asleep after midnight, while folks in their 40s go to bed earlier but devote the fewest hours to sleep.
That might not be surprising, especially to 40-something parents of teens. But the study gives a clearer picture of Americans' sleep habits, by using objective measures instead of self-reports: Participants wore devices on their wrists that recorded their movement, day and night, for seven days.
The findings are based on more than 11,000 Americans aged 6 and up who took part in a periodic federal health study between 2011 and 2014. And many of the results did support what past studies have shown.
Yes, school-age children - especially teenagers - stay up late. In fact, one-quarter of 14- to 17-year-olds didn't fall asleep until midnight over the weeklong period.
Given that they were typically getting up around 7 a.m. on school days, that's notable, according to researcher Shaoyong Su, a genetic epidemiologist at the Medical College of Georgia, in Augusta.
Teens do try to make up for it on the weekends, typically sleeping for an extra hour and 15 minutes. But regularly being short on sleep can rack up a sleep "debt" that's hard to surmount.
It's not clear, Su said, what teenagers' sleep debt might mean for their longer-term health. But in the short term, their school performance and emotional well-being might suffer.
Meanwhile, the study found, college-age Americans (18 to 25 years) get to bed even later, with one-quarter typically falling asleep around 1 a.m.
"I see this all the time," said Dr. Fariha Abbasi-Feinberg, a sleep medicine specialist at Millennium Physician Group in Fort Myers, Fla.
She said biology is likely part of the story, as the body's circadian rhythm does shift in adolescence. But many kids and young adults may also be staying up late staring at the glowing light of an electronic device.
Abbasi-Feinberg, who is also on the American Academy of Sleep Medicine's board of directors, noted that the study data were collected about a decade ago - which, when it comes to devices and social media, is almost ancient history.
"These days, kids are getting devices at an earlier age," Abbasi-Feinberg said. "The question is: How will this affect how they're growing up, including their sleep?"
As for adult Americans, they typically sleep the fewest hours around age 40, dipping below eight hours a night, on average.
Actual sleep needs are pretty stable across adulthood, Abbasi-Feinberg said, so that mid-life nadir likely reflects what's going on in people's lives: balancing work and home responsibilities, and trying to juggle your own schedule as well as your kids'.
Americans' sleep duration does gradually increase after age 50. Again, that makes sense, Abbasi-Feinberg said, since that's a time when the nest empties and people eventually retire.
For old people, in particular, health conditions can also be a factor in longer sleep times, according to Su and his colleagues.
Age is not the only factor in sleep patterns, however. The study found that Black Americans generally get the least sleep, and have the latest sleep times, compared with all other racial groups.
Both Su and Abbasi-Feinberg pointed to the "social determinants" that may be driving that finding. If, for example, you live in a neighborhood, building or home that exposes you to noise or artificial light from outside, it is probably tough to fall asleep and stay asleep.
How do you know when your sleep habits are not ideal?
If you nod off within minutes of sitting down, that's a red flag, said Dr. Vaughn McCall, a co-researcher on the study and chair of psychiatry and health behavior at Medical College of Georgia.
"You should be able to stay awake during a college lecture even if the lecture is boring," he said.
For some people, the solution is simply a matter of prioritizing sleep, Abbasi-Feinberg said.
"Is it necessary to catch up on Netflix? Can you cut back on social media time?" she said. "Sleep is not the thing we should skimp on."
Turning off the devices before bedtime - and the blue light that stimulates the brain - may make it easier to fall asleep. But it's also important, Abbasi-Feinberg noted, to be exposed to natural light in the morning, to set the body clock on the right path.
If you do get a solid eight hours of sleep yet still feel groggy during the day, it's wise to talk to your doctor, Abbasi-Feinberg said. That can be a sign of a health condition, such as sleep apnea.
The National Sleep Foundation recommends that adults under age 65 get seven to nine hours of shut-eye each night. Older adults may need a bit less - seven to eight hours.
The findings were recently published online in Scientific Reports.
The National Sleep Foundation has more on healthy sleep habits.
SOURCES: Shaoyong Su, PhD, genetic epidemiologist, Georgia Prevention Institute, Medical College of Georgia, Augusta; Vaughn McCall, MD, chairman, psychiatry and health behavior, Medical College of Georgia; Fariha Abbasi-Feinberg, MD, medical director, sleep medicine, Millennium Physician Group, Fort Myers, Fla., and member, board of directors, American Academy of Sleep Medicine, Darien, Ill.; Scientific Reports, May 10, 2022, online