Sleep expert Matthew Walker is not a fan of the expression “you can sleep when you’re dead.”
In fact, he calls it “mortally unwise advice.”
“Sleep is Mother Nature’s best effort yet to counter death,” Walker says.
He would know. Walker, who is director of the University of California, Berkeley’s Center for Human Sleep Science, has been studying sleep for more than 20 years and is the author of a new book, “Why We Sleep: Unlocking the Power of Sleep and Dreams.”
Walker’s work centers around a major and often overlooked problem: many Americans are sleep-deprived. One in three U.S. adults report they usually get less than the recommended seven hours, according to the Centers for Disease Control and Prevention.
This could be harming peoples’ health in myriad ways, Walker said: Insufficient sleep is linked to everything from Alzheimer’s disease to stroke, cancer and even suicide, and it doesn’t take that much lost sleep — just a loss of one hour in one single night.
That’s pushed Walker, who allots himself a “non-negotiable” eight hours of sleep each night, to become something of a sleep warrior.
“Once you know the science, you honestly wouldn’t be doing anything else,” he said.
Walker spoke with MarketWatch by telephone from the University of California, Berkeley, where he’s a professor of neuroscience and psychology, about what people get wrong about sleep, how to get a better night’s slumber and his stance on naps.
Below is an edited version of the conversation.
MarketWatch: What is the biggest misconception people have about sleep?
Matthew Walker: They have so many misconceptions. I think people probably don’t recognize the full deathly and disease-related consequence of insufficient sleep.
People dramatically underestimate how much sleep is linked to all the diseases killing us. We know a lack of sleep is linked to numerous forms of cancer — bowel, prostate, breast cancer.
They may not understand how little sleep reduction it takes. For example, if I put a somewhat healthy individual who has no history of diabetes on one week of five to six hours of sleep, by the end of that week their blood sugar is disrupted so profoundly that they would be classified by their doctor as pre-diabetic.
You don’t need to be going for one week on six hours — all it takes is one hour across one single night.
MarketWatch: So how many hours should we be getting?
Walker: Below seven hours of sleep, there are objective impairments in the body. Eight hours are recommended.
MarketWatch: What about people who say they can survive on fewer hours of sleep?
Walker: Based on the science, you can make somewhat clear statements: The number of people who can survive on six hours of sleep without impairment is zero.
The problem is this: That your subjective sense of how well you’re doing without sufficient sleep is a miserable predictor of objectively how well you’re doing. In other words: You don’t know that you’re sleep-deprived, even if you’re sleep deprived. It’s like with a drunk driver — ‘I know that you think you’re fine to drive, but objectively you’re not fine to drive.’
Survive is not the word you want to be using in life. Those people who say ‘I’m just fine on five to six hours of sleep’ — you may think that but unfortunately, that’s objectively, scientifically not true. And if you fight biology in that way, biology usually wins. And the way you know you’ve lost that battle is sickness and disease.
MarketWatch: How do certain medical conditions factor into this? What sleep recommendations do you have for individuals with them?
Walker: Certainly sleep disorders are a problem — there are well over 100 types. Aging is a big problem, menopause is a marked and known problem; pregnancy is a real problem, both during and after. I think people need to be especially mindful during those times of trying to protect their sleep and encourage sleep.
This is not an endorsement of sleeping pills — they do not produce naturalistic sleep, and are associated with higher risk of death and cancer. The American College of Physicians said in 2016 that sleeping pills must not be the first-line treatment for sleep problems. Instead, first-line should be cognitive behavioral therapy — it’s just as effective as sleeping pills in the short term, but lasts much longer.
There are also five things people can do to improve their sleep, not unique to any one condition — anyone can do them. They are principles I adhere to as well.
- Regularity: Go to bed at the same time and wake up at the same time, whether it’s a weekday or weekend, or you’ve had a good or bad night of sleep.
- Darkness: We are a dark-deprived society — we need darkness to release a hormone called melatonin, which helps the onset of your sleep. Try to limit screen time, turn down the lights in your house — you don’t need half of them on in the hour before bed. You’ll start feeling sleepier as a consequence.
- Temperature: We evolved to use the drop in temperature at night to help instruct our sleep. Your core body temperature has to drop two to three degrees Fahrenheit. A cold room is moving you in right temperature direction for good healthy sleep. When we came into the modern era, we actually dislocated ourselves from the beautiful thermal ebb and flow of our environment.
- Don’t sit in bed awake: Many people make this mistake. Your brain is an incredibly associative device and quickly learns that being in bed means being awake. After 20 minutes, get up, go to the other room, and under a dim light, read a book. Only return to bed when you’re sleepy. You’ll relearn the association of your bed being about sleep.
- Caffeine: No caffeine after about 2 p.m. and don’t go in with a nightcap — no alcohol. Caffeine we all know keeps us awake. It’s the most traded commodity after oil, which tells us everything about our state of sleep deprivation. The danger there is even if you fall asleep and stay asleep, the depth of sleep you have isn’t going to be as deep as if you hadn’t had that cup of coffee. Now you’re reaching for two cups instead of one, developing a dependency, an addiction cycle. Alcohol is probably the most misunderstood drug when it comes to sleep. It’s a sedative, and sedation is not sleep, you’re not putting yourself in a naturalistic sleep. It will fragment your sleep, and you’ll wake up many times at night and feel unrefreshed the following day.
MarketWatch: What should people who don’t feel refreshed when they wake up do?
Walker: They should ask themselves: Are you drinking too much caffeine, or occasionally having a glass of wine or beer with dinner or a nightcap in the evening? Are you looking at screens before bed?
Another aspect is to think about whether or not you suffer from snoring. One of the principal sleep disorders is actually sleep apnea, which simply means an absence of breath. There are lots of free apps that can listen by your bedside to whether or not you’re snoring.
MarketWatch: How bad are screens? If you just check your phone right before bed, can that disrupt a whole night’s sleep?
Walker: We actually don’t know if that brief a burst of light is damaging. The problem with that is if you’re not putting your phone on airplane mode it causes sleep procrastination — you’re there in bed, and start using your device, make a Facebook post, ‘I should order that thing from that store;’ you’re already half an hour deficient in your sleep.
It also causes anxiety, just knowing that device is there for you, waiting to sort of explode with the world in the morning. When people have some kind of anxiety thing going on the next day, the depth of their deep sleep is not as deep because of hyped anxiety that is there, and we create a low-grade form of that anxiety with our phones resting by our bedside.
MarketWatch: What about naps — are you pro or con?
Walker: We’ve done a lot of work in this area at my sleep center: Naps do give benefits; they can enhance learning and memory, lower blood pressure, improve emotional stability and decision making.
But they are a double-edged sword. While you’re awake, the chemical melatonin builds up in your brain and creates sleepiness, so you should be able to fall asleep naturally. When we sleep, we release that pressure, almost like a valve on pressure cooker. If you nap in the afternoon for example, you’re going to release the sleepiness pressure, so when it comes time to fall asleep in the evening you struggle.
If you don’t have any problems falling asleep and staying asleep and you can nap regularly, naps are okay.