Editor's note: This popular story from the Daily Briefing's archives was republished on Dec. 9, 2020.
Sleep is essential to good health—yet many people have misconceptions about what makes for a good night's sleep, and some of those beliefs can be dangerous to public health, according to a study published last week in Sleep Health.
For the study, researchers from NYU Langone Health searched 8,000 websites to round up the 20 most-common beliefs about healthy sleep habits.
The researchers then asked a panel of sleep experts to rate each statement by level of falseness and importance to public health. Both were rated on a scale from one to five. On the truth assessment, a lower score represented a truer belief and a high score represented a belief that's more false. On the public health effects assessment, the higher the score, the greater the significance to public health.
Out of the 20 myths the researchers found, here are the five that represent the greatest threats to public health, listed in order of significance.
Myth 1: Adults need only 5 or less hours of sleep for general health
According to senior study investigator Girardin Jean-Louis, a professor at NYU Langone's population health department, "A lot of people felt less than five hours of sleep a night was just fine," a finding he described as the "most problematic assumption we found."
According to CDC, adults are supposed to get between seven and 10 hours of sleep each night, depending on their age. However, CDC has found that one-third of Americans sleep less than seven hours each night.
According to Rebecca Robbins, a postdoctoral research fellow at NYU Langone's population health, department, "We have extensive evidence to show that sleeping five hours a night or less, consistently, increases your risk greatly for adverse health consequences, including cardiovascular disease and early mortality."
Myth 2: While annoying, loud snoring is mostly harmless
The researchers also discovered that snoring was viewed as "mostly harmless" in their searches.
According to the National Heart, Lung, and Blood Institute, "loud, raucous snores interrupted by pauses in breathing" is a sign of sleep apnea, a sleep disorder that puts you at an increased risk for heart attacks, atrial fibrillation, asthma, high blood pressure, glaucoma, cancer, diabetes, kidney disease, and cognitive and behavioral disorders.
"Sleep apnea is extremely exhausting," Robbins said. "These patients sleep and then they wake up over and over; then they are fighting sleep all day long because they're so exhausted. It's also very underdiagnosed. We believe it affects about 30% of the population, and around 10% are diagnosed."
Myth 3: Your brain and body can adapt and work just as well with less sleep
The researchers noted that it's possible that you might "adjust" to less sleep, but doing so comes "at the risk of serious health consequences."
That's because body goes through four distinct phases of sleep to restore itself—and the later stages have the biggest health benefits. In the first stage, you sleep lightly, then in the second stage you become disengaged from your environment.
In the third and fourth stages, you begin to enter your deepest sleep, which is where rapid eye movement (REM) comes in, generally about 90 minutes after you fall asleep.
While sleeping, your body will go through several REM cycles. You'll also enter deep sleep, in which your brain waves will slow down into what are called delta waves. It's during this stage that memories are processed and human growth hormone is released.
"The deeper stages of sleep are really important for generation of neurons, repairing muscle and restoring the immune system," Robbins said.
Myth 4: Being able to sleep anytime anywhere is a sign of a healthy sleep system
If you find that you're able to fall asleep anywhere at any time of the day, that doesn't mean you're well-rested—in fact, it means just the opposite, the researchers wrote. It can also be a sign that you may have sleep apnea.
"Falling asleep instantly anywhere, anytime, is a sign that you are not getting enough sleep and you're falling into 'micro sleeps' or mini-sleep episodes," Robbins said. 'It means your body is so exhausted that whenever it has a moment, it's going to start to repay its sleep debt."
Myth 5: Drinking alcohol before bed will improve your sleep
Having a "nightcap" of alcohol before bed can cause "sleep disturbances in the second half of the night" and "dela[y] the onset of REM sleep," the researchers wrote. It can also "worsen sleep apnea symptoms."
According to Robbins, alcohol "dramatically reduces the quality of your rest at night. It continues to pull you out of [REM] and the deeper stages of sleep, causing you to wake up not feeling restored" (May, USA Today, 4/17; LaMotte, CNN, 4/17; Crist, Reuters, 4/19; ScienceDaily, 4/16; Robbins et al., Sleep Health, 4/16).
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