Hey, sleepyheads. What you believe about sleep may be nothing but a pipe dream.
Many of us have notions about sleep that have little basis in fact and may even be harmful to our health, according to researchers at NYU Langone Health’s School of Medicine, who conducted a study published Tuesday in the journal Sleep Health.
“There’s such a link between good sleep and our waking success,” said lead study investigator Rebecca Robbins, a postdoctoral research fellow in the Department of Population Health at NYU Langone Health. “And yet we often find ourselves debunking myths, whether it’s to news outlets, friends, family or a patient.”
Robbins and her colleagues combed through 8,000 websites to discover what we thought we knew about healthy sleep habits and then presented those beliefs to a hand-picked team of sleep medicine experts. They determined which were myths and then ranked them by degree of falsehood and importance to health.
Here are a few very wrong, unhealthy assumptions we often make about sleep, an act in which we spend an estimated third of our lives — or, if we lived to 100, about 12,227 combined days.
Stop yawning. It’s time to put these unsound sleep myths to bed.
- Adults need five or fewer hours of sleep
“If you wanted to have the ability to function at your best during the day, not to be sick, to be mentally strong, to be able to have the lifestyle that you would enjoy, how many hours do you have to sleep?” asked senior study investigator Girardin Jean-Louis, a professor in the Department of Population Health.
“It turns out a lot of people felt less than five hours of sleep a night was just fine,” he said. “That’s the most problematic assumption we found.”
We’re supposed to get between seven and 10 hours of sleep each night, depending on our age, but the US Centers for Disease Control and Prevention says that a third of Americans sleep fewer than seven hours a night. According to World Sleep Day statistics, sleep deprivation is threatening the health of up to 45% of the global population.
“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,” Robbins said.
In a longitudinal study of 10,308 British civil servants published in 2007, researchers found that those who reduced their sleep from seven to five hours or fewer a night were almost twice as likely to die from all causes, especially cardiovascular disease.
Science has also linked poor slumber with high blood pressure, a weakened immune system, weight gain, a lack of libido, mood swings, paranoia, depression and a higher risk of diabetes, stroke, dementia and some cancers.
- It’s healthy to be able to fall asleep ‘anywhere, anytime’
Falling asleep as soon as the car/train/airplane starts moving is not a sign of a well-rested person, sleep experts say. In fact, it’s just the opposite.
“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.”
You feel sleepy because of a buildup of a chemical called adenosine in the brain, which happens throughout the day as you head toward night. Sleeping soundly reduces that chemical so that when you wake up, the levels are at their lowest, and you feel refreshed.
But the longer you stay awake and the less sleep you get, the more your adenosine levels rise, creating what’s called a sleep load or sleep debt.
Want to check your level of sleepiness? Look at the Epworth sleepiness scale, and if you’re worried, check in with a sleep doctor who can do more extensive testing in a sleep lab.
- Your brain and body can adapt to less sleep
People also believed that the brain and body could adapt and learn to function optimally with less sleep. That too is a myth, experts say. That’s because your body cycles through four distinct phases of sleep to fully restore itself.
In stage one, you start to lightly sleep, and you become disengaged from your environment in stage two, where you will spend most of your total sleep time. Stages three and four contain the deepest, most restorative sleep and the dreamy state of REM, or rapid eye movement sleep.
“During REM, the brain is highly reactive,” Robbins said. “It almost looks like your brain is awake if we hook you up to two more electrodes and were able to monitor your brain waves.”
REM can occur any time during the sleep cycle, but on average, it starts about 90 minutes after you’ve fallen asleep. REM is when your body and brain are busy storing memories, regulating mood and learning. It’s also when you dream. Your arm and leg muscles are temporarily paralyzed during REM sleep, so you can’t act out your dreams and injure yourself.
Because a good night’s sleep gives your sleep cycle time to repeat, you’ll go through several REM cycles, which take up about 25% of your total sleeping time.
Another important stage of sleep is deep sleep, when your brain waves slow into what is called delta waves or slow-wave sleep. It’s the time when human growth hormone is released and memories are further processed.
“The deeper stages of sleep are really important for generation of neurons, repairing muscle and restoring the immune system,” Robbins said.
It’s tough to wake a person from deep sleep. If you do wake, you can feel groggy and fatigued; mental performance can be affected for up to 30 minutes, studies show.