You're Probably Wrong about How Much You Sleep
Research shows many of us over- or underestimate our ZZZs.
Which person are you in the morning?
— "I got plenty of sleep last night.''
— "I didn't sleep a wink, just tossed and turned all night."
Either way, it's a decent bet you don't really have a clue about how much or how well you actually slept.
Most of us either overestimate or underestimate our hours of sleep, scientists say. Here are the details — and how technology could help.
Chronic insomniacs often think they barely nod off night. Some of them are right — but others are wrong.
In one study, researchers looked at 142 confirmed insomniacs and 724 non-insomniacs. Everyone took a standard personality test. Then they underwent sleep studies during which their brain waves and heart rate were recorded to find out how long they slept. The researchers divided them into two groups: people who slept more than six hours and people who slept less.
Insomniacs who got more than six hours of sleep thought they got less. These underestimators also were more likely to have higher depression and anxiety scores and lower “ego strength" on the personality test.
The authors conclude, “Anxious-ruminative traits and poor resources for coping with stress seem to mediate the underestimation of sleep duration.”
Insomniacs aren't the only ones who underestimate their sleep, says Alon Avidan, MD, MPH, a professor of neurology and director of the University of California Los Angeles Sleep Disorders Center. Those who have sleep state misperception do so, too, Avidan says.
"The patient thinks they are not sleeping well, whereas in reality they are sleeping very well," he says. "That is something that we often see in our clinic." These patients may think they have slept one hour, and it's actually three, they discover in the sleep disorders center. Their sleep may be light, he says, so the patient may feel unrested and conclude he hasn’t slept.
For other underestimaters, the ''honor'' of claiming you don't get much sleep — because you're busy and important, of course — may also come into play. That thinking should be discouraged, experts agree, since lack of sleep is linked with weight gain, high blood pressure, shorter life span and diabetes.
Many others overestimate the amount of sleep they get, says Avidan. In the study mentioned above, people who slept less than six hours thought they got more sleep than they really did (they overestimated). In another study of than 2,000 men and women, people overestimated their sleep time by 16 minutes on average.
In yet another study, scientists asked some 600 men and women ages 18 to 30 to estimate their sleep, keep a sleep log and wear a wrist actigraph, a device that records movements to estimate sleep. The average measured sleep was six hours, but the men and women reported they slept nearly an hour longer. Those who slept five hours reported an average of 6.3 hours. Those who slept seven reported 7.3.
Why are we so off? Avidan says it's simply human nature. "We are very poor judges,'' he says, with most of us not in tune with how rested or sleepy we really are.
If you think you've slept enough and you haven't, ''you may have daytime sleepiness," says Avidan. That can make you hazardous on the road, he says, and perhaps unproductive on the job.
So how much is enough?
For adults, seven to eight hours is recommended, according to the National Institutes of Health. Teens need nine or ten, school age children, ten hours or more. Preschoolers should sleep 11 or 12 hours, and newborns, 16 to 18 hours.
Related: America, Home of the Sleep-Deprived?
Technology to the rescue?
In recent years, a host of smart phone apps and trackers has sprung up to help you assess your sleep right in your own bed. Some track total sleep time and tell you how long it took you to fall asleep. Others tell you how much you tossed and turned during the night.
How accurate are they? "We don't have good data on these wearable devices," Avidan says. Many track movement, he says, ''and movement may or may not correlate with sleep." For instance, he says, some people who toss and turn may actually be asleep when they’re doing it. Others may be awake but motionless, and the device ''reads'' this as sleep.
As the devices improve, so may their accuracy, Avidan says. But it’s brain wave activity, not motion, that sleep specialists measure in sleep labs to evaluate sleep, he says.
Even so, sleep apps and tracking programs may help by emphasizing the need for good sleep. Using them may encourage poor sleepers to improve their sleep habits, Avidan says.
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