Does Listening To Your Body Lead To Better Sleep?

Listen to your body.

We hear that a lot. Hydrate if you're thirsty. Ease up when your hamstrings ache. Don't ignore those chest pains.

Unfortunately, technology can make listening to your body complicated, if not dangerous.

Ultra-processed foods are a good example. Companies like Frito-Lay spend millions of dollars each year ensuring that their products are biochemically irresistible. Listening to your body clamor for Cheetos may lead you on a path straight to obesity and heart disease.

As for sleep, we may find it disrupted by work, stress, restless bed partners, and crying babies, but technology can interfere too. Screen use before bed suppresses the production of melatonin, delaying the onset of sleep and undermining its quality. Turn off the devices, experts say, and you'll sleep better. Your body knows what to do.

Is the story really that simple? Or, as with ultra-processed foods, is our "natural" desire for sleep so conditioned by technology that by the end of the day, what feels best might not be the healthiest strategy?

In this newsletter I'll be stitching together some very different sorts of data of relevance to this question.

I'll start by discussing what it would mean to listen to your body's demands for sleep.

Later, I'll introduce a new study conducted among the BaYaka, a group of hunter-gatherers who live in the Congo Basin. This study offers a glimpse into sleep patterns in a society devoid of sleep-influencing technologies such as alarm clocks, artificial lights, and screens.

Chronotype

If you listen to your body's desire for sleep, what you'll "hear" is your chronotype.

"Chronotype" refers to natural preferences for the timing of sleep. Being a morning person is one kind of chronotype; being a night owl is another.

It's convenient to divide people into categories such as larks vs. owls, but the data suggest that chronotype is a matter of degree. I'd call myself a morning person, for instance, but in my case that means I'm up by 6 or 6:30 a.m. and feeling good. Others wake around 5 a.m. and feel just as good.

Chronotype is genetically-based, grounded in circadian rhythms, and essentially impossible to change. In ideal circumstances, our chronotype aligns with our actual sleep patterns. Larks thrive on early work schedules and relatively early bedtimes. Owls flourish to the extent they can do everything later.

When a person's sleep habits clash with their chronotype, they experience "social jetlag" and an elevated risk of problems such as obesity, metabolic syndrome, and depression.

In short, to the extent that life permits, you should listen to your body's demands for sleep – i.e., your chronotype.

Or should you?

Some nuance

A study published by Stanford researchers last summer showed that going to bed later, after around 1 a.m., increased the risk of mental health problems, regardless of chronotype.

In this study, both larks and owls suffered from staying up later. At the same time, owls who managed to get to sleep earlier showed better mental health. In their case, misalignment between chronotype and sleep was actually good for them.

This was a large study (73,888 adults from the UK Biobank database) and the methodology was strong, but one detail is especially important: The researchers focused exclusively on diagnosed mental health problems such as generalized anxiety disorder and depression.

In other words, the data doesn't speak to psychological functioning in general. Rather, it links particularly late bedtimes to higher rates of mental illness.

I reached out to Jamie Zeitzer, the senior author on the study and a professor in the Department of Psychiatry and Behavioral Sciences at Stanford. I was curious whether he thought the findings would generalize to less serious problems. Simply put, he does:

"I think we would find similar trends in non-pathological behaviors or outputs, including general mood and energy."

However, Dr. Zeitzer added an important qualification. What's problematic is not the lateness of the hour per se. Rather, staying up late and doing certain kinds of activities may exacerbate an existing tendency toward poorer mental health. Here's how Zeitzer put it:

"Despite our recent results, I still believe that there is nothing intrinsic about being an owl that leads to poorer mental health outcomes. Rather (though at this point we don't have direct proof), I think that particular behaviors that are conducive to worse mental health are facilitated by being awake late and without good social support. Larks who get up early also have this kind of isolation, but it is at the beginning of the day, where your brain may be operating differently...So...yes, I think that the near infinite space of entertainment possibilities facilitates our staying up later than we might have otherwise and without doing so in a way that is positive to mental health (staying up late with friends, I believe, is very different than staying awake late doomscrolling or watching Netflix)."

This tracks with my personal experience. As a lark, I never feel lonely or depressed at 6 a.m. The world is still quiet, but it brims with possibilities. I run, I read, I enjoy the coffee, I work on this newsletter.

On the other hand, when I stay up past midnight or 1 a.m., I rarely feel good or sleep well unless it's people rather than screens that have kept me up.

Here's my takeaway from Dr. Zeitzer's remarks and from the scholarly literature more broadly: Chronotype is fixed. You can't really change it. But it's worth trying to adjust your sleep schedule, to the extent possible, to align with your particular chronotype. And, if you happen to be an owl, you should avoid staying up excessively late. Owls should consider the possibility that solitary time in front of a screen may be the least healthy way of spending those late hours.

Questioning the concept of chronotype

Everything I've written so far comes from research and theory carried out in technology-rich societies. But listening to our bodies (i.e., our chronotypes) may not be optimal if the messaging has been disrupted by technology.

We might ask then: What would life be like without screens, not to mention alarm clocks, artificial lights, and other kinds of technology that influence sleep? Would our bodies still be delivering the same messages?

Sleep research suggests at least that people would still differ from each other in when we fall asleep and wake up, because we're born with different chronotypes.

In fact, according to the "sentinel hypothesis", differing chronotypes are the product of natural selection. We're a diurnal species – more active during the day than at night – but sleeping in the dark leaves us vulnerable to predators. The survival of our species was supported by different members of our immediate group being alert at different times during the night. In short, the larks and the owls need each other.

For this reason, I was surprised to see a study, published last week in Scientific Reports, that seems to question the basic premise of innate chronotype differences.

A new study

This study, led by Dr. Luke Kretschmer at University College, London, was conducted among the BaYaka, a small group of hunter-gatherers who live in the rainforests of the Congo Basin.

The BaYaka subsist on hunting, fishing, and gathering foods such as yams and caterpillars. Children in the BaYaka group that Kretschmer and colleagues studied do not attend school.

In short, this is a society with no alarm clocks or schools, and, after the sun sets, no source of light other than the moon, stars, and small campfires. You might say that apart from the campfires, technology has essentially no influence on the sleep patterns of the BaYaka.

Since the researchers were interested in the activity levels of BaYaka youth, they persuaded 51 young people to wear accelerometers on their wrists for two to six days.

An accelerometer is a small device that records changes in the speed and direction of movement. Although not infallible, accelerometers provide fairly accurate guidance as to when the wearer falls asleep and wakes up. (The devices provided to the BaYaka were waterproof and worn 24/7. They emit no light.)

Sleep-related findings

Kretschmer and colleagues reported that adolescents fell asleep later than children did, but that all BaYaka, regardless of age, woke up around sunrise.

The fact that adolescents fell asleep later isn't surprising. It's well-known that a natural, hormone-driven phase delay causes teenagers to fall asleep later than they did as children (and will do as adults).

What does seem surprising is that BaYaka teens still woke up early. Assuming that phase delay, we'd expect them to both fall asleep later and wake up later. In other words, like teens in other societies, we'd expect them to have become more owlish.

On the face of it, Kretschmer and colleagues' data suggests that without the accoutrements of modern life, including electricity and screens, we'd fall asleep by the firelight and wake up with the sunrise. That sounds so....healthy. It also hints that our technologies create or at least exacerbate chronotype differences.

However, there are a few details missing from the picture. Are BaYaka teens awakened each morning by others? Do they feel drowsy during the day? I reached out to Dr. Kretschmer but haven't heard back.

I did get a chance to communicate briefly with Dr. Kristen Knutson, a professor of neurology and preventive medicine at Northwestern University and a prominent sleep scholar. Dr. Knutson hadn't read the study, but she raised the same sorts of questions about the data:

"What I wonder is whether the adolescents in that culture are required to wake at sunrise (e.g. family/community members waking them). Alternatively, the environment may make sleeping past sunrise more difficult (light, noise, temperature) even if people are not forcing them to wake up. It is difficult to measure all the socio-cultural-environmental factors that shape our sleep patterns, but that doesn't mean they aren't there or should be dismissed. And there is no way to measure "sleep need" directly. The circadian phase delay in adolescents has been replicated in so many studies it seems to be a true biological phenomenon."

In other words, BaYaka adolescents probably experience a phase delay, just like teens everywhere else, but their environment doesn't allow them to sleep in.

After all, humans are social animals. Very few of us get to "listen to our bodies" exclusively while ignoring everyone around us.

Meanwhile, a close look at Kretschmer and colleagues' data reveals that they overlooked signs of chronotype differences.

Specifically, what Kretschmer and colleagues recorded are mean sleep and wake times. On average, BaYaka adolescents fall asleep around 9:46 p.m. and wake up around 5:49 a.m. The researchers emphasized the consistency of these times. However, the standard deviations around those means are slightly more than one hour apiece.

In other words, there's actually a fair amount of variation in exactly when BaYaka adolescents fall asleep and when they wake up. They're clearly not even close to sleeping and waking in unison.

Bottom line: I see no evidence here that in a pre-industrial society, we would all simply fall asleep when it gets dark and then wake up with the light. Rather, we are made up of larks and owls, and everything in between. Listening to our bodies would mean understanding our own chronotypes and sleeping at times that vary from one person to the next. There's no evidence here that technology has artificially created chronotype differences.

What can we learn from the BaYaka?

As with other hunter-gatherer societies, BaYaka of all ages are more physically active during the day than their counterparts in industrialized societies. Typically they have little or no exposure to ultra-processed foods. For these and other reasons, they have exceptionally low rates of problems such as obesity, type 2 diabetes, and hypertension.

We might say too – and this is more speculative – that their sleep patterns are healthier. Average sleep and waking times of 9:46 p.m. and 5:49 a.m. indicate that the BaYaka tend to sleep both earlier and a bit longer than folks in industrialized societies.

We also have problems with sleep debt – sleep deprivation on weekdays owing to work and other social obligations – which some of us compensate for via extra sleep on the weekends. Studies show that weekend catch-up can offset sleep lost during the week, but this strategy doesn't work well when sleep deprivation is chronic.

This is not to say that the BaYaka are generally more healthy than we are. Other studies estimate their infant mortality rate at around 20%, or about 40 times higher than the current rate in the U.S., and in many cases the deaths are attributable to infectious or parasitic diseases that would be preventable here.

We might say instead that there are tradeoffs. The BaYaka benefit from healthy diets and more physically active lifestyles, for instance, while missing out on some of the benefits of western medicine. We gain much from digital technologies, but those very technologies can work against our chronotypes and undermine our bodies' messaging.

Napping is a good example. If your body says sleep and you take a three-hour nap, you may disrupt your circadian rhythms and struggle to fall asleep at night. But why did your body crave such a long nap? Could it have been the technological distractions of the previous night (social media, gaming, the latest episode of Severance, etc.)?

In this scenario, the healthiest strategy is to not listen to your body. And the best way to do that is to rely on more technology. Specifically, an alarm. Set it for 20 or 30 minutes and you'll probably wake up refreshed without risking impaired sleep later that night.

This is an example of how technology can solve the problems technology creates. Obviously the healthier approach would be to avoid screens late at night in the first place.

In sum, listening to your body can promote healthier sleep, but only if we keep in mind that technology can affect the messaging. Blue light from screens can affect melatonin levels, delaying sleep when our bodies most need it, then undermining the quality of sleep once we finally do drift off.

Final thought

I've referred here to larks and owls. There are other distinctions floating around, but I don't think that finding the label that best fits you is as useful as becoming sensitive to the nuances of your chronotype and how to sleep in the way makes you feel most refreshed and energized when you're awake.

For instance, I'm a morning person, but I also get a second wind in the late evening. Afternoons, I've learned, are my zombie hours. I find this observation much more useful than simply thinking of myself as a lark.

Thanks for reading – and I hope you rest well tonight!