We have long known that sleep is of profound importance to health. It is a requirement for living, much like breathing, but with awake and asleep playing out over longer spans and to slower rhythms than inhalation and exhalation. Sleep is essential. We must turn off if we are to go on.
Unlike many of the factors that affect health profoundly, the impact of sleep is both immediate and intimate. You have no need of me, or clinical trials, to tell you that sleep matters. All of us have, at some time, slept well — and awakened to feel the invigoration of having done so. All of us have, and most of us, alas, too often do, sleep poorly or too little — and thus know all too well that feeling of a head stuffed overfull with cotton and far too heavy for our necks.
While we need no science to tell us sleep matters, science can enhance our understanding of all the reasons why. Over recent years, no doubt due largely to our preoccupation with the epidemic obesity we keep choosing to lament rather than fix, the links between sleep and weight have received particular attention.
Relevant research consistently associates sleep deprivation with obesity risk, and invokes a number of potential mechanisms. Some are fairly self-evident. For instance, lack of sleep tends to mean lack of energy, which is apt to discourage exercise. Sleep deficiency also tends to produce irritability, and all the wrong foods tend to provide, albeit briefly, all the right comfort to dull this pain.
Some mechanisms are less apparent, and likely more important. The quantity, quality and timing of our sleep are tethered to our endocrine system. The circadian rhythms of our hormones influence our capacity to sleep and wake, and are in turn influenced by them. Disruptions in sleep patterns inevitably disturb hormonal balance, which in turn reverberates through the endocrine system like ripples in a pond. Cortisol levels are perturbed, unbalancing levels of insulin, and subsequently, appetite-regulating hormones such as leptin and ghrelin. Brain neurotransmitters, several of which double as hormones, are affected as well, including norepinephrine and serotonin. The stress of sleep deficiency stimulates epinephrine release. The result in general is increased appetite, an increased tendency to store calories as fat around the middle where it does the most harm, increased inflammation and the initial steps toward insulin resistance.
We knew all of this from a large and growing body of research addressing sleep. But relatively little of that research is of the direct cause-and-effect variety in people, because it’s challenging to randomize people to different sleep patterns for extended periods.
A new study in Pediatrics is something of an elegant exception, and all the more so for being carried out in children. While most of us adults would likely welcome more and better sleep, kids tend to go the other way — so they lack our bias. For research purposes, that’s a good thing — even if it’s not so good when it makes bed time a battle. I’ve got five kids. I know that gig.
In the new study, researchers assessed appetite, hormone levels, weight and food intake in a group of roughly forty children ages 8 to 11. They randomized the kids to a sequence of different number of hours in bed within a reasonable range, and monitored brain waves to tally hours actually slept. In one assignment, the kids had an extra 90 minutes in bed for a week. In the other, they lost 90 minutes. The result, measured by EEG, was an average of more than two hour differences in sleep time between assignments.
The effects on all measures of interest were clear and compelling. Two hours less sleep, even without rising to the definition of sleep “deprivation” was still enough to disrupt hormone levels, increase hunger and appetite, and increase daily calorie intake. In the sleep reduction phase of the trial, fasting leptin (a hunger suppressing hormone) levels were lower; reported food intake was higher; and weight increased slightly. And again, this was in kids — who may if anything be less prone to treat sleep-related irritabilities with food than we are.
The new study doesn’t change what we thought we knew, but it certainly lends emphasis. The physiologic effects of even moderate changes in nightly sleep time are rather potent, directly relevant to the prevailing health problems of our time, and nearly immediate.
Sleep has long been on my short list of top priorities for health, even if I’m slightly less good at it than I am with all the others. If it isn’t on yours, I certainly think it should be. Any parent or grandparent concerned about weight gain or diabetes risk in a child they love now has cause to make it a priority for those children, too. As a society subject to epidemic obesity and diabetes in children and adults alike, we may have new reasons to cultivate the respect for sleep it clearly deserves.
Action items begin there, with respecting sleep as much more than down time. Busy people may feel they don’t have time to sleep. However, for sustained productivity, let alone health, the truth is that none of us has time not to sleep.
At times, sorting out sleep problems may require assistance — such as undergoing polysomnography to identify sleep apnea. But often, the problem is behavioral and under our own control. There is a simple skill set for optimizing sleep hygiene, which any of us can learn and practice to good effect.
Finally, there is an important argument here for approaching our health holistically. Perhaps you want to lose weight or avoid diabetes — you could decide, reasonably, to focus on diet and exercise. But if you ignore other aspects of your health, such as sleep, your own daily routine may conspire against your objectives. A culture widely prone to both obesity and sleep deprivation may be a quintessential case of meeting the enemy, and finding it is us.
I have seen just such patterns in my practice over the years, and a holistic view of health, orchestrating into a logical sequence of tweaks, can be just the fix. Often, with the requisite insights and skillpower, you can oversee just such troubleshooting on your own — no docs or drugs required.
We can’t be too busy to get the sleep we need, unless we are also too busy to get the health and weight control we want. If you remain unconvinced, I can only think to suggest you sleep on it.
David L. Katz is the founding director, Yale-Griffin Prevention Research Center. He is the author of Disease-Proof: The Remarkable Truth About What Makes Us Well.