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October 11 - October 18, 2025
“If sleep does not serve an absolutely vital function, then it is the biggest mistake the evolutionary process has ever made.”II
sleep is the single most effective thing we can do to reset our brain and body health each day—Mother Nature’s best effort yet at contra-death.
sleep is the state we must enter in order to fix that which has been upset by wake. But what if we turned this argument on its head? What if sleep is so useful—so physiologically beneficial to every aspect of our being—that the real question is: Why did life ever bother to wake up? Considering how biologically damaging the state of wakefulness can often be, that is the true evolutionary puzzle here, not sleep.
sleep was the first state of life on this planet, and it was from sleep that wakefulness emerged.
Sleep is of such vital necessity that no matter what the evolutionary demands of an organism, even the unyielding need to swim in perpetuum from birth to death, Mother Nature had no choice. Sleep with both sides of the brain, or sleep with just one side and then switch. Both are possible, but sleep you must. Sleep is non-negotiable.
If you sleep-deprive this sparrow in the laboratory during the migratory period of the year (when it would otherwise be in flight), it suffers virtually no ill effects whatsoever. However, depriving the same sparrow of the same amount of sleep outside this migratory time window inflicts a maelstrom of brain and body dysfunction. This humble passerine bird has evolved an extraordinary biological cloak of resilience to total sleep deprivation: one that it deploys only during a time of great survival necessity.
What becomes clearly apparent when you step back from these details is that modern society has divorced us from what should be a preordained arrangement of biphasic sleep—one that our genetic code nevertheless tries to rekindle every afternoon. The separation from biphasic sleep occurred at, or even before, our shift from an agrarian existence to an industrial one.
those that abandoned regular siestas went on to suffer a 37 percent increased risk of death from heart disease across the six-year period, relative to those who maintained regular daytime naps. The effect was especially strong in workingmen, where the ensuing mortality risk of not napping increased by well over 60 percent.
Autistic individuals show a 30 to 50 percent deficit in the amount of REM sleep they obtain, relative to children without autism.III Considering the role of REM sleep in establishing the balanced mass of synaptic connections within the developing brain, there is now keen interest in discovering whether or not REM-sleep deficiency is a contributing factor to autism.
Alcohol is one of the most powerful suppressors of REM sleep that we know of.
What emerges from all of these studies is that REM sleep is not optional during early human life, but obligatory. Every hour of REM sleep appears to count, as evidenced by the attempt by a fetus or newborn to regain REM sleep when it is lost.X Sadly, we do not yet fully understand what the long-term effects are of fetal or neonate REM-sleep disruption, alcohol-triggered or otherwise. Only that blocking or reducing REM sleep in newborn animals hinders and distorts brain development, leading to an adult that is socially abnormal.
Passing into your mid- and late forties, age will have stripped you of 60 to 70 percent of the deep sleep you were enjoying as a young teenager.
reach seventy years old, you will have lost 80 to 90 percent of your youthful deep sleep.
the parts of our brain that ignite healthy deep sleep at night are the very same areas that degenerate, or atrophy, earliest and most severely as we age.
“As a pianist,” he said, “I have an experience that seems far too frequent to be chance. I will be practicing a particular piece, even late into the evening, and I cannot seem to master it. Often, I make the same mistake at the same place in a particular movement. I go to bed frustrated. But when I wake up the next morning and sit back down at the piano, I can just play, perfectly.”
Glial cells are distributed throughout your entire brain, situated side by side with the neurons that generate the electrical impulses of your brain. Just as the lymphatic system drains contaminants from your body, the glymphatic system collects and removes dangerous metabolic contaminants generated by the hard work performed by neurons in your brain, rather like a support team surrounding an elite athlete.
during sleep that this neural sanitization work kicks into high gear.
In what can be described as a nighttime power cleanse, the purifying work of the glymphatic system is accomplished by cerebrospinal fluid that bathes the brain. Nedergaard made a second astonishing discovery, which explained why the cerebrospinal fluid is so effective in flushing out metabolic debris at night. The glial cells of the brain were shrinking in size by up to 60 percent during NREM sleep, enlarging the space around the neurons and allowing the cerebrospinal fluid to proficiently clean out the metabolic refuse left by the day’s neural activity. Think of the buildings of a large
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Should you experimentally prevent a mouse from getting NREM sleep, keeping it awake instead, there is an immediate increase in amyloid deposits within the brain. Without sleep, an escalation of poisonous Alzheimer’s-related protein accumulated in the brains of the mice, together with several other toxic metabolites. Phrased differently, and perhaps more simply, wakefulness is low-level brain damage, while sleep is neurological sanitation.
Inadequate sleep and the pathology of Alzheimer’s disease interact in a vicious cycle. Without sufficient sleep, amyloid plaques build up in the brain, especially in deep-sleep-generating regions, attacking and degrading them. The loss of deep NREM sleep caused by this assault therefore lessens the ability to remove amyloid from the brain at night, resulting in greater amyloid deposition. More amyloid, less deep sleep, less deep sleep, more amyloid, and so on and so forth.
The fatal final straw turned out to be septicemia—a toxic and systemic (whole organism) bacterial infection that coursed through the rats’ bloodstream and ravaged the entire body until death. Far from a vicious infection that came from the outside, however, it was simple bacteria from the rats’ very own gut that inflicted the mortal blow—one that an otherwise healthy immune system would have easily quelled when fortified by sleep.
Weak immune systems are a known consequence of insufficient sleep, as we have discussed in great detail. I should also note that one of the most common immune system failures that kills individuals in hunter-gatherer clans are intestinal infections—something that shares an intriguing overlap with the deadly intestinal tract infections that killed the sleep-deprived rats in the above studies.
natural sleep is one of the most powerful boosters of the immune system, helping ward off infection.
The less sleep you have had, or the more fragmented your sleep, the more sensitive you are to pain of all kinds.
NICUs that have implemented dim-lighting conditions during the day and near-blackout conditions at night. Under these conditions, infant sleep stability, time, and quality all improved. Consequentially, marked and significant improvements in neonate weight gain and significantly higher oxygen saturation levels in blood were observed, relative to those preterms who did not have their sleep prioritized and thus regularized. Better still, these well-slept preterm babies were also discharged from the hospital several weeks earlier!
This silent sleep loss epidemic is one of the new public health challenges we face in the twenty-first century in developed nations. If we wish to avoid the suffocating noose of sleep neglect, the premature death it inflicts, and the sickening health it invites, a radical shift in our personal, cultural, professional, and societal appreciation of sleep must occur.
