Eye-opening Sleep Science
The scoop on sleep from the world’s number one sleep expert, Dr. Matthew Walker
Dr. Matthew Walker, a scientist and professor of neuroscience and psychology at the University of California, Berkeley, is considered by many to be the leading authority on the crucial role sleep plays in health and disease. It affects every body system, including respiratory, cardiac, hormonal, and immune functions, and ultimately may dictate how well we age.
One thing that science has clearly settled: sleep-deprived people run a higher risk of most diseases. Yet for many, a good night’s sleep is elusive, as evidenced by global sleep-aid spending of $67.76 billion in 2024, projected to reach $113.61 billion by 2033.
A vocal and enthusiastic advocate, Dr. Walker has devoted his career to studying sleep and has created the “4 Pillars of Good Sleep” framework to achieve the ultimate restful and healthy sleep. “QQRT” stands for quantity, quality, regularity, and timing. He sees these tenets as the four legs of a chair, and if any one of them becomes unstable, the chair will topple over.
He recently sat down with Steven Bartlett for the second time on the Diary of a CEO podcast to discuss the latest scientific research, some of which challenges conventional wisdom, and its impact on the ever-evolving world of sleep.
Prioritize practices
My overarching takeaway from the nearly two-and-a-half-hour discussion is that, more than any pill or supplement we can take, our lifestyle choices determine how well we sleep and whether the “4 Pillars” will topple or stay steady. In fact, when explicitly asked about what supplements he recommends, Dr. Walker said it’s a bit like stepping over dollars to pick up pennies; first, focus on the foundation of good sleep.
Dr. Walker stresses the importance of making these choices just as high a priority in our lives as diet or exercise, and designing our days accordingly.
This was an affirmation of some of what I’ve discovered through my own sleep journey, and while I still have a way to go to get that perfect night’s sleep, I’m confident I’m on the right track.
Quantity: the eight-hour myth
The long-standing and ubiquitous recommendation of 8 hours of sleep is now considered outdated rubbish. Instead, science points to an optimal spread of 7-9 hours for overall good health. Although there are some people on the internet who point to a minimum of 6 hours as statistically insignificant relative to 7 hours for all-cause mortality rates, Dr. Walker is quick to point out the difference between surviving and thriving.
Statistically speaking, people who get only 6 hours of sleep may have just as long a life as those who sleep 7-9 hours, but the quality of their lives will be very different.
That being said, there is a subset of people who have a particular “sleep gene” that allows them to sleep 6 hours (or just under) with absolutely no negative health impact. But before you jump to thinking that may be you, the likelihood you are in the rarified group is 0.0064%—the same chance as getting hit by lightning!
Quality is as important as quantity
While the quantity of sleep has hogged the spotlight, quality is just as important for predicting all-cause mortality and mental well-being.
This is defined by two markers. The first measurement, which can be assessed at home with sleep trackers, is the continuity or efficiency of sleep, monitoring whether you sleep in one or two nice, long bouts (high-quality sleep) versus very fragmented, fitful sleep (very poor quality). The second measurement, which is assessed in the lab, evaluates the quality of strong, slow brainwaves of deep non-REM sleep. This deep non-REM sleep is the third stage of sleep, during which the body repairs injuries and reinforces the immune system. You spend the most time in deep sleep during the first half of the night, with periods getting shorter as the night goes on.
But those shorter periods of REM in the early morning hours are critical, so don’t shortchange your early morning sleep if you can at all help it.
Regularity and timing are crucial
Moving on to the third and fourth pillars of QQRT, Dr. Walker was converted and convinced of the importance of the regularity of sleep time, thanks to the UK Biobank Study. This study looked at a cohort of 60,000 individuals and found that the group that had a regular bedtime of plus or minus 15 minutes—meaning they went to bed within a 30-minute window every night—had a 49% relative decrease in all-cause mortality, a 39% cancer mortality risk reduction, and a 57% cardiometabolic disease risk reduction.
Even for the consummate researcher, these findings were stunning and cemented the idea that regularity was a powerful sleep fundamental and a highly predictive factor across many forms of mortality.
Personally, I’m an annoying creature of habit and go to bed like clockwork between 8:00 and 8:15, the latest by 8:30. My husband Andrea, jokes that I’ll turn into a pumpkin if I don’t get in bed on time, but now my body is so conditioned that I really do feel like I’m turning to jello if I’m tardy.
Scarcity of darkness
With QQRT providing a firm foundation, Dr. Walker has additional recommendations to support good sleep. Controlling our evening light is a critical tool in his quality sleep toolbox.
He firmly believes that, in this modern world, “we are a dark-deprived society.” He characterizes the majority of our nighttime light as “junk light” that fools the brain into thinking it’s still daytime outside.
Remember, our circadian rhythm, the body’s master 24-hour clock, is inextricably tied to the light entering our eyes. With the intensity of many of the LED lights in our homes, our natural sleep cues can be entirely thrown out of whack.
One hour before bed, Dr. Walker switches off his home’s main lighting and dims the remaining ones to a glow. This is one of the easiest and most accessible fixes we can implement.
Nighttime digital is more impactful than blue light
A highly influential study published 10 years ago found that blue light from an iPad disrupted the body’s melatonin production, impairing sleep. Even after people stopped using the device, the blast radius's impact on dream sleep lasted a week. Hundreds of thousands of yellow-tinged, blue-light-blocking glasses later, new scientific information suggests the extent of blue-light disruption may be a fallacy.
Michael Greta, a relentless Australian researcher, has been trying to replicate the landmark findings without success. He discovered that, with phones and tablets in particular, the core problem is not the blue light they emit but the high brain activation, both through the content they provide and the stress they produce. As Dr. Walker stated, “these devices that we use are attention-capture devices, and they are designed to fleece you of your attention economy. And they do it ruthlessly, spending tens of millions of dollars designing products to do that.”
Dr. Walker readily admits that blue light plays a role in sleep, but it’s just one element of a broader lighting issue that is robbing people of quality restful sleep. He recommends a digital detox for a couple of hours before bedtime, as doomscrolling can lead to “bed-rotting” that mutes your sleep and creates a vicious cycle that traps people in perpetually insufficient sleep.
I put my phone face down on our “drop zone” cabinet (where we put keys, mail, and such) about 6:30ish and only glance at it once for any pertinent messages before going to bed. It’s now part of my nighttime routine. I haven’t missed anything life-altering since adopting the habit, but I have gained the ability to fall asleep faster and stay asleep longer.
Melatonin’s limited efficacy
Drug store shelves are overflowing with sleep-aid products containing melatonin, but did you know that the ingredient has a fairly limited use, which means people may not be solving their sleep problems the way they hoped?
Simplistically, melatonin’s primary role is to regulate our circadian rhythm and tell our body it’s time to sleep. It is a hormone that our body naturally produces, with production rising 1-3 hours before bedtime, peaking at night, and dropping during the day. Dr. Walker’s view is that while melatonin is helpful for jet lag when our bodies are out of their usual rhythm, outside that application, studies show it increases sleep efficiency by only a paltry 2.2% and that regular users risk “confusing their morning brain into a dense nighttime fog.”
Instead, he recommends augmenting our natural melatonin production with adequate morning sunlight (at least 10-15 minutes) and sleep-forward lifestyle choices, such as the QQRT pillars.
Beds are for sleeping
If you suffer from insomnia, your brain may be conditioned to it. Dr. Walker explains that our brains are incredibly associative devices and learn associations. So, if you watch TV, scroll on your phone, eat, or catch up on work in bed, the next time you go to bed, your brain thinks “sleep, tv, sleep, scroll, sleep, eat, sleep, work, sleep, awake.”
The better rule of thumb is if you are still awake after 20 minutes, get out of bed (keep the lights dim) and sit in a comfy spot to read, listen to a podcast, music, whatever is relaxing. Once you feel tired, head back to bed. Condition your mind, and your body will follow.
Undersleep causes belly fat
This is so interesting. I’ve heard that poor sleep adds to obesity, but Dr. Walker clarified why. When you are sleep-deprived, your body metabolizes calories as fat rather than storing them, for example, as glycogen in the muscles.
To shine a spotlight on this, there was a study that comprised people who were dieting and either getting sufficient sleep or not getting sufficient sleep. Although both groups lost weight, the critical metric was what they were losing. For those who were not getting sufficient sleep, 70% of the weight they lost came from lean muscle mass, not fat.
In other words, when you are not getting sufficient sleep, you keep what you want to lose, which is fat, and you lose what you want to keep, which is muscle. Oh. My. Gosh. We need all the muscle mass we can have as we age!
Sleep is our superpower
I’ve called sleep our superpower before, not realizing it’s the title of Dr. Walker’s TED talk as well! Great minds… Anyhoo, it simply cannot be overstated how vital sleep is to our overall health, in fending off disease and living well, aging great.
If you are interested in developing the best sleep of your life, pick up his best-selling book, Why We Sleep; catch him on his eponymous The Matt Walker Podcast; or peruse his website, The Sleep Diplomat.
Here’s to happy and healthy sleep!