Matt Walker says some brain regions are up to 30% more active during REM sleep than during waking.
“That stage of sleep, some parts of your brain are up to 30% more active than when you're awake.”
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Matt Walker
2 episodes · 46 quoted claims
Matt Walker says caffeine's half-life in the average adult is about five to six hours.
“the half-life is somewhere between five to six hours, and the quarter-life, therefore, is somewhere between ten to twelve hours.”
Matt Walker says the average adult's biological clock runs about 24 hours and 13 minutes.
“It's about, um, about twenty four hours and thirteen minutes, I think was the last calculation.”
Matt Walker cites a meta-analysis finding melatonin increased total sleep by 3.9 percent in healthy adults.
“melatonin will only increase total amount of sleep by 3.9 minutes on average, minutes, not even minutes. No, percent.”
Matt Walker says studies found melatonin's sleep benefits at doses of 0.1 to 0.3 milligrams.
“the optimal doses for where you do get sleep benefits in the populations that we've looked at are somewhere between 0.1 and 0.3 milligrams of melatonin.”
Matt Walker says NASA pioneered nap research in the 1990s with astronauts.
“NASA pioneered this back in the 1990s, and during the missions, they were experimenting with naps for their astronauts.”
Matt Walker says NASA found 26-minute naps improved mission performance by 34 and alertness by 50.
“naps of little as 26 minutes improved, um, uh, mission performance by 34, and improved daytime alertness by 50.”
Matt Walker describes a study where alcohol before sleep cut growth hormone release by more than 50%.
“There was well over 50%, five zero drop in their growth hormone release during alcohol-laced sleep at night.”
Matt Walker describes a Harvard study finding REM sleep was the strongest sleep-stage predictor of lifespan.
“If you look at the contribution of different s sleep stages to your lifespan, REM sleep was the strongest predictor of your longevity.”
Matt Walker says each extra hour of sleep raised women's interest in intimacy by 14 percent.
“for every 1 hour of sleep extra sleep that a woman gets, her interest in becoming sexually intimate with her partner increases by 14”
Matt Walker says studies found a worry journal cut the time to fall asleep by about 50%.
“they found that keeping one of those journals decreased the time it takes you to fall asleep by 50% to five zero.”
Matt Walker says a UC Berkeley study by Alison Harvey found counting sheep made falling asleep harder.
“Alison Harvey, and they found that counting sheep actually made it harder to fall asleep.”
Matt Walker describes an occupational study where workers moved near windows slept over 30 minutes longer with 5 to 10 percent better sleep efficiency.
“I think the increase in total sleep time was well over thirty minutes, and the improvement in sleep efficiency was five to 10%.”
Matt Walker cites a study of over 20 melatonin brands where actual content ranged from 83 percent less to 478 percent more than labelled.
“it ranged from, I think it was 83 less than what it said on the bottle, to 478 more than what it said on the bottle.”
Matt Walker says five of seven good studies of valerian root found no sleep benefit and two were inconclusive.
“Five of the seven found no benefit, uh, of valerian root on sleep, then two out of the seven, the data was just insufficient.”
Matt Walker says two tart cherry juice trials found sleep increases of 34 and 84 minutes.
“it increased the amount of sleep that you got by 34 minutes, the other, it increased the amount of sleep that you got by 84 minutes”
Matt Walker says the brain paralyses the body during REM sleep so dreams are not acted out.
“The brain paralyzes the body so that the mind can dream safely.”
Matt Walker says his research found no major psychiatric disorder in which sleep is normal.
“there is no major psychiatric disorder that we can find in which sleep is normal.”
Matt Walker says the one magnesium study showing sleep benefit involved older adults with insomnia who were probably magnesium deficient.
“my guess is that because it's an older community as well, they were probably probably deficient in magnesium”
Matthew Walker cites the RAND Corporation as finding that insufficient sleep costs most nations about 2% of GDP, which was $411 billion in the United States.
“insufficient sleep costs most nations about 2% of their GDP. So here in America, that number was $411 billion of lost profit caused by insufficient sleep.”
Matthew Walker says average nightly sleep in the UK is six hours forty-nine minutes and in Japan six hours twenty-two minutes, the worst of the three countries he compared.
“In the U. K, it's not much better, six hours and forty nine minutes. Japan was the worst, six hours and twenty two minutes.”
Matthew Walker says caffeine has a half-life of about five to six hours, meaning half of it is still in the body after that time.
“caffeine has what we call a half-life of about five to six hours. In other words, after about five to six hours, half of that caffeine is still in your system.”
Matthew Walker says that in studies a standard dose of caffeine reduced participants' deep sleep by roughly 15 to 30%.
“it will strip away your deep sleep by about somewhere between fifteen to 30%”
Matthew Walker describes a Harvard Medical School study in which reading on an iPad before bed, compared with a book in dim light, delayed falling asleep.
“reading for an hour on an iPad just before bed, relative to just reading a book in dim light. Firstly, it delayed the time with which people fell asleep”
Matthew Walker says the iPad-reading group in the Harvard study had melatonin release delayed by about ninety minutes to two hours.
“it delayed the release by about somewhere between ninety minutes to two hours across the individuals.”
Matthew Walker credits Maiken Nedergaard of the University of Rochester with discovering the brain's glymphatic cleaning system.
“this is a stunning discovery made by a scientist called Megan Nedergaard at the University of Rochester here in America.”
Matthew Walker says the brain's cleaning system is called the glymphatic system, named after the glial cells that form it.
“It's called the glymphatic system, named after these glial cells that make it up.”
Matthew Walker says the American College of Physicians convened an expert panel in 2016 to review the evidence on classic sleeping pills, and it advised against making them first-line treatment for insomnia.
“in 2016, the American College of Physicians, they had a expert panel who surveyed all of the literature on classic sleeping pills.”
Matthew Walker says NASA research in the 1980s found that naps of twenty minutes to an hour raised task productivity by about 34% and alertness by over 50%.
“these naps, anywhere between twenty minutes to an hour, could increase productivity on these different tasks by about 34% and increase general alertness by over 50%.”
Matthew Walker says the meditation app Calm was rescued by introducing sleep stories, which helped it reach a valuation above $1 billion.
“the meditation company Calm, you know, was saved by the the introduction of sleep stories into their app.”
Matthew Walker says a UC Berkeley study by Allison Harvey found that mentally walking a familiar route in detail halved the time it took people to fall asleep, while counting sheep slowed it.
“sure enough, people fall asleep in about 50% less time, half the time it takes.”
Matthew Walker says that in sleep-restriction studies the fullness hormone leptin fell by 18% and the hunger hormone ghrelin rose by 28%.
“That signal of fullness, satiation, was decreased by 18%. If that wasn't bad enough, ghrelin, which is the hunger hormone, that leapt up by 28%.”
Matthew Walker says that when dieting while underslept, about 60% of the weight lost comes from lean muscle rather than fat.
“you're not getting sufficient sleep, then 60% of all of the weight that you lose will come from lean muscle mass”
Matthew Walker says sleep-deprived people's endocannabinoids, the body's own cannabis-like compounds that stimulate appetite, rose by over 20%.
“these naturally occurring endocannabinoids rocketed up by over 20%, cranking up people's appetite.”
Matthew Walker says junior doctors finishing a thirty-hour shift are 168% more likely to have a car accident.
“they finish that thirty hour shift and get back in their car, they are 168% more likely to get into a car accident because of their lack of sleep.”
Matthew Walker says a survey of medical curricula across several countries found doctors receive only about an hour to ninety minutes of sleep education in medical school.
“most doctors will only be given about an hour to an hour and a half of sleep education during their entire medical school education.”
Matthew Walker says that after losing a full night of sleep, several recovery nights restore only about four to four and a half of the eight hours lost.
“you'll maybe only sleep back about four, four and a half of the eight hours that you lost.”
Matthew Walker says research found that an extra hour of sleep raised women's desire to be intimate with a partner by 14%.
“if a woman gets an hour of extra sleep, her libido desire to be intimate with her partner increases by 14%.”
Matthew Walker says surveys in the UK and US found that about one in four people sleep in a different location from their partner.
“One in four people will say that they sleep in different locations with their partner, so almost a quarter of people in relationships will sleep in different locations.”
Matthew Walker says at least twenty-two genes determine whether a person is a morning type, evening type or in between.
“right now there's at least twenty two different genes that dictate what you are morning type, evening type, or somewhere in between.”