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Two Important Sleep Discoveries
A simple tool to get more out of your sleep, in addition to a study that gives peace of mind to people who don’t get enough sleep.
I suspect most of you never spent a lot of time considering a sleep mask.
Me neither.
They’re something women named Tallulah wear, or maybe women of libidinous nature in general who tiptoe home at dawn, heels in hand, and, lacking a dark, cozy coffin to crawl into, don a sleep mask to block out the cursed light while they rest until darkness falls and they can again prowl the earth.
But really, other than day sleepers, who wears those things? Unless your bedroom is so electron-ified that it’s lit up like the command center for the Artemis moon mission, shouldn’t your g-damn eyelids shut out the light?
That’s what I used to think. It turns out, though, that completely blocking out ambient light by wearing a sleep mask improves memory and alertness the following day. At least that’s what two new concurrently conducted studies revealed.
The idea of wearing a sleep mask may seem weenie to you, but I offer up the age-old wisdom that’s been tossed in the face of every naysayer since the dawn of invention:
“Hey, I know, but if it works…”
Also, I wouldn’t be laying this info on you if I hadn’t tried it for several weeks and found that sleep masks do seem to have merit. (I like this one the best.)
A Midsummer Night’s Dream
The authors of the study, researchers from the U.S., Italy, and England, set out to explore “how wearing an eye mask to block light during overnight sleep impacts memory and alertness, changes that could benefit everyday tasks like studying or driving.”
The first study included 89 adults aged 18 to 35 and was conducted during the summers of 2018 and 2019. (Summer months were chosen because the researchers suspected the masks would be more useful when the sun came up early.) All were asked to wear masks at night for a week.
The subjects’ sleep-replenishing qualities during this mask-wearing phase were then compared to what they experienced when they then slept without a mask for a week, or, alternately, how well they slept while wearing a mask with holes (to factor in whether any discomfort caused by the mask skewed the results) the week after the mask-wearing week.
The subjects were then challenged with word-association tasks and tests that measured reaction times (the Psychomotor Vigilance Test, or PVT, and a motor-skill learning analysis, or MSL). Tests were conducted on the last two days of each mask/no-mask week.
Experiment 2 was conducted over the summer of 2020 and consisted of four nights (two for habituation, i.e., getting used to the masks, and two spent conducting experiments). The study involved 33 adults between the ages of 18 and 35, all of whom were wired up with devices to measure brain activity while they slept.
So Maybe Batman’s Mask is a Sleep Mask?
“Our results demonstrate that wearing an eye mask during an overnight sleep can facilitate both new learning and alertness the next day,” concluded the researchers.
To be specific, the participants performed much better in PVTs, which can transfer over to real-world activities like driving, sports performance, or any activities that require rapid responses. Mask wearers also displayed superior memory performance.
Interestingly, these increases in performance don’t appear to be directly related to sleep quality. If anything, wearing a mask was obviously more uncomfortable than going without, but it didn’t impact self-reported assessment of how well participants slept or morning alertness.
Instead, the researchers speculate that wearing an eye mask increased time spent experiencing slow-wave activity (SWA), which is kind of where nature empties the brain’s cache of memes and assorted superfluous crap and then restructures the “files.” During SWA sleep, saturated synapses are scaled down and their capacity to encode new information is restored, hence better memory and improved reaction times.
“Enhanced” Sleep, but Not Necessarily Better Sleep Quality
While not explicitly discussed in their paper, the definition of a dark room is open to interpretation. We may turn the lights off, but in many cases, there must still be enough light pollution leaking through the drapes and enough light from the glow of multiple electronic devices to affect the time we spend in SWA sleep.
Hence the use of a sleep mask seems a simple hack to ensure enhanced sleep. And, at least from this writer’s experience, a sleep mask does seem to affect sleep quality as I found myself waking up fewer times at night.
But this simple sleep hack may offer little help to those that are crappy sleepers in general. To them, a mask most likely won’t prove to be much of a sleep hack at all. Crappy sleepers, even though they might not feel horrible all the time, no doubt worry about the effects of chronically poor sleep on their health, whether that poor sleep be from work demands, social desires, or demons that keep them awake at night. If that’s you, take heart because the results of another study may offer you some comfort.
Can Training Mitigate the Negative Health Effects of Rotten Sleep?
Yeah, you know that not getting enough sleep can, if it continues long enough, contribute to heart disease and cancer, as can physical inactivity. Both topics have been studied extensively, but rarely has anyone looked at the synergistic effects of these separate mortality factors.
The good news is that someone’s finally compared the two head-to-head and done it right. This new long-term study of 380,000 men and women in the United Kingdom directly compared quality of sleep (using complex categorizations of sleep characteristics) to complex categories of physical activity.
The great news is that physical activity may be able to counter the negative health effects of poor sleep, which I find comforting. In other words, you may be cursed with rotten sleep abilities, but as long as you’re exercising, the effects may cancel out, i.e., the very fact that you exercise may save you from the horrible health repercussions of sleep-deprivation.
“Metabolic Equivalent Task Minutes” vs. Sleep Quality
The participants were interviewed and filled out questionnaires, along with having various physical measurements taken to determine their baseline health condition, their level of physical activity, and sleep behaviors.
Their physical activity was assessed using “metabolic equivalent task minutes (MET),” where the minutes roughly equate with number of calories expended per minute of physical activity. The numbers were determined by multiplying the MET value of the activity by the number of physical activity ¶ hours per week. The categories broke down as follows:
High (1200 or more MET-minutes per week)
Medium (600 to less than 1200 MET-minutes per week)
Low (0 to less than 600 MET-minutes per week)
They then came up with a novel scale to determine sleep quality. The sleep “score” was comprised of five sleep characteristics: chronotype (night owl vs. annoying morning person tendencies), sleep duration, presences of insomnia, daytime sleepiness, and snoring. Participants were given values between 0 and 5.
Poor sleepers were those that earned a 0 or 1; intermediate sleepers scored between 2-3; and healthy sleepers got a 4 or higher.
The researchers then used these scoring methods, combined with information from the questionnaires and interviews, to come up with a dozen physical activity/sleep combos.
Then came the morbid part: The scientists tracked the participants’ health until May 2020, or, of course, until they died. They were interested in death from any cause, but deaths from cardiovascular disease (coronary heart disease and stroke) or cancer in particular caught their analytical eyes.
Some Comforting Findings
Approximately 15,500 participants died during the study: 4095 succumbed to CVD and 9064 to cancer, while 1932 died from coronary heart disease, 359 from hemorrhagic stroke, 450 from ischemic stroke, and 1595 from lung cancer.
We thank them for their service.
As you likely guessed, the lower a participant’s sleep score, the higher their risk of death from any cause, and poor sleep combined with little-to-no physical activity? Dead man, or dead woman, walking.
But yeah, no surprise. And sure, you’d likely expect that regular physical activity helped mitigate the detrimental effects of rotten sleep, but the degree to which it helped was surprising. Here, I’ll let the researchers say it themselves:
“Compared with no MVPA (moderate-to-vigorous physical activity), levels of physical activity at or above the lower threshold recommended by the WHO (600 MET-mins/week), appeared to eliminate most of the detrimental associations of poor sleep and mortality.”
You catch that? They’re suggesting that a moderate amount of physical activity put the kibosh on the detrimental effects of rotten sleep. That means all you lifters/exercisers out there, assuming you’re expending the bare minimum of effort/time in the gym, are helping to bullet-proof yourself against the ill effects of poor sleep.
And yes, this was just an observational study, but it was a large one, and sure, if horrible sleep persists for years, all bets are likely off, regardless of exercise habits.
Still, this study gave me some comfort, as a bad night’s sleep often gave me the same kind of gnawing feeling I’d get if I knew I was running my car a half-quart short of oil. Oh, I knew in the short run that it wouldn’t cause any harm, but it sure as hell wasn’t good for the engine in the long run.
A Pressure Relief Valve
Sleep is a funny thing – the more you want it, the more elusive it is. However, this study about physical activity and sleep takes some of the pressure off. If I can’t get to sleep right away, it isn’t as much of a concern anymore. I know that my morning workout will act as a mortality Band-Aid, and, if I wear my sleep mask, I’ll enhance whatever sleep hours I do manage to get in.
For more tips, check out 26 Sleep Hacks: What Works, What Doesn’t.
References
References
Viviana Greco, et al, Wearing an eye mask during overnight sleep improves episodic learning and alertness, Sleep Research Society, 15 December 2022.
Bo-Huei Huang, et al, Sleep and physical activity in relation to all-cause, cardiovascular disease and cancer mortality, BMJ, 2022;56:718-724.
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