How many hours of sleep did you get last night? You probably don’t realise it, but your answer to that question could potentially tell you a lot about what’s going on inside your body. It’s well known that people who are very physically active typically need more sleep than sedentary people, seeing as their bodily systems need peace and rest in order to recuperate between workouts. It’s also well established that age is an important determinant of sleep needs, with infants and kids needing more sleep than adults. Finally, everyone knows that there’s some inter-individual variability in sleep needs, with different people having somewhat different sleep requirements.
What a lot of people don’t know, however, is that our sleep needs are also affected by the workings of our immune systems.
An inflamed, unhealthy body needs more sleep than a healthy one
Not so long ago I put up an article here on the site entitled Hunter-gatherers Don’t Get 8 Hours of Sleep a Night. Should You?. In that article I briefly mentioned a recent study showing that hunter-gatherers such as the Hadza don’t get more sleep than industrialized people. On average, they only sleep about 6 hours.
That probably comes as a surprise to a lot of people, seeing as ancestral health enthusiasts have long promoted the idea that hunter-gatherers “sleep like babies”. The longstanding dogma is that our Paleolithic forebears got 7-9 hours of high-quality sleep each night.
In the aforementioned article I looked into the question of whether our sleep needs differ from that of hunter-gatherers and other traditional people and talked about the different factors that affect our sleep requirements. One of the factors I mentioned was immune status. In the 8 months that have passed since then, I’ve become increasingly more convinced that immune status is an important determinant of sleep needs. It may in some respects be even more important than physical activity levels, genetics, and age.
As I pointed out in the article in which I discussed the sleep habits of hunter-gatherers, a solid body of research supports the idea that people who are inflamed typically need more sleep than people who aren’t. Both acute and chronic inflammation seems can raise one’s sleep needs.
One doesn’t have to have a PhD in immunology to understand why this is the case. A body that is inflamed doesn’t prioritize processes related to reproduction, brain function, and athletic performance; rather, it allocates energy and resources to turning out the inflammatory fire that’s burning inside it and recovering homeostasis. It prefers to rest, sleep, and take it easy as opposed to moving and being active, seeing as the former activities promote healing and recovery. Moreover, the risk of additional immune insults is lower in bed than outside in the big, scary world.
It’s unfortunate that many health practitioners pay little or no attention to these things, seeing as an understanding of these facets of the human biology can enhance our understanding of human health and disease. A health practitioner who has recognized that immune status is an important determinant of energy levels and sleep needs can more easily pinpoint what’s wrong with his patients. He’s better able to make correct diagnoses and prescribe the correct treatment to each individual patient.
What happens when the inflammatory fire never stops burning?
In some cases, the long list of disturbances and problems that accompany inflammation are quickly resolved. In other cases, however, things never come to an end: the inflammatory fire keeps burning indefinitely.
Unfortunately, this seems to be what’s happening inside the body of many modern humans (1, 2, 3). Chronic, low-grade inflammation doesn’t have such an immediate and dramatic impact on a person’s health and well-being as severe, acute inflammation, but it does cause subtle shifts in various biological processes and greatly raises one’s risk of developing a variety of health problems. Moreover, as pointed out earlier, it affect one’s sleep needs.
I strongly suspect that one of the reasons why hunter-gatherers don’t get or need that much sleep is that they tend to be very healthy. Unlike obese, doughnut-eating westerners, they don’t have a disturbed microbiota, a leaky gut, elevated levels of various fatty substances in their blood, or poor insulin and leptin sensitivity.
Hunter-gatherers live in a very different environment than we do. In other words, we shouldn’t automatically assume that we – contemporary humans – have similar sleep needs as they do. We’re not as physically active as they are; however, our bodies are more inflamed; hence, we may require more sleep than they do.
The notion that there is an association between sleep needs and immune status is not only supported by research studies (e.g., 4, 5, 6, 7), but also by anecdotal reports. Personally, I’ve found that I typically require a lot more sleep during periods when my immune system is acting up and responding to something it perceives as foreign and dangerous, as opposed to during periods when it’s calm and relaxed. I’m sure you’ve experienced the same; however, you may not have noticed it. If you think back to the last time you got the flu, were food poisoned, or otherwise got sick, you may remember that those events affected your sleep needs.
Most likely, those troubles were temporary rather than permanent and your immune system found its way back to a homeostatic state quite quickly. Not everyone is so lucky though…
People who suffer from Chronic Fatigue Syndrome (CFS) and other disorder that have chronic inflammation at their roots typically require more sleep than healthy folks. Their immune systems are in a constant state of warfare; hence, it’s not surprising that these people are “always” tired and need a lot of sleep. It’s exactly what one would expect to see, given that there’s an intimate link between immune status and sleep needs.
Unfortunately, many health professionals don’t realise that these patients could greatly benefit from inflammation-resolving therapies. As I’ve pointed out earlier here on the site, mismatch resolution, including microbiome restoration, should be very high on the list of priorities for any health professional who deals with inflamed patients.
Beside physical activity levels, age, and genetics, immune status is a very important determinant of sleep needs. Inflamed, unhealthy people typically require more sleep than healthy folks, seeing as their bodies need rest in order to resolve proinflammatory processes and regain homeostasis. One of the main reasons why hunter-gatherers don’t sleep that much is likely that they are healthy and fit, as opposed to unhealthy and chronically inflamed.
If you feel chronically tired, need a lot of sleep, and/or have trouble getting out of bed in the morning, then chances are your body is inflamed. You don’t necessarily suffer from a severe infection, but the levels of various proinflammatory cytokines in your bloodstream are probably somewhat elevated. By taking steps to cool down your body, you will not only become more energetic and vibrant, but you’ll likely find that you don’t need as much sleep as before.
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