How Much Sleep Is Too Much Sleep?

Illustration: Sam Woolley, Gizmodo

An entire industry—with its own spokespeople, podcasts, best-sellers, retreats, truisms, etc.—has sprung up around sleep. Give or take a contrarian or two, the message of most of this stuff seems to be that sleep is good and that if you’re not sleeping seven or eight hours a night, you should be. And since you’re probably not sleeping seven or eight hours a night—since, in all likelihood, you can barely focus on this sentence, having sacrificed one or two or all of your needed eight hours to soothing your newborn, or streaming bad TV, or snorting cocaine—what all this stuff is really saying is: sleep more.

But how much is too much, sleep-wise? It is possible to go overboard, or is sleep one of those things, like eating well, or not erupting in rage at friends and loved ones, to which moderation does not really apply? As we learned from the host of sleep experts we reached out to for this week’s Giz Asks, this is a somewhat controversial question in the field of sleep studies. But the good news is that if you’re worried you’re sleeping too much, you probably aren’t—unless you’re still always tired, in which case you very well might have a severe clinical disorder. Could go either way!

Shelby Harris

Clinical Psychologist, Associate Professor, Neurology and Psychiatry, Albert Einstein College of Medicine, and Director of the Behavioural Sleep Medicine Program at Montefiore Medical Center

The vast majority of people—approximately 70%—need between six and nine hours of sleep a night. If you’re someone who needs more than nine hours on a regular basis, you might want to think about how restful your sleep is and if it is of good quality. Some people just require more sleep than others do, but there are many people who sleep long hours and are still excessively sleepy due to various sleep disorders. You might need to go see someone about snoring, or anything that might be going on in the middle of the night that might be interrupting your sleep, as one reason people will sleep longer is that the sleep they’re getting at night is just not refreshing, so they’re craving it more. If you find, though, that you can’t get to work or school because you are continually sleeping through your alarm, despite getting a full night’s sleep every night, definitely see a sleep specialist for a consultation.

One way to tell how much sleep you need is to actually take a week off of work if you can do it. Go to bed at your usual time, but don’t set an alarm in the morning. The first few days, you’re usually paying back a sleep debt, but by day four or five you should can get a good estimate of how much sleep you need, by averaging together how much sleep you’ve been getting the next few nights.

I always tell people to think about how you feel during the day. Don’t judge by how you feel right when you wake up—wait an hour, and if you feel rested and refreshed for most of the day (we all have dips here and there), you’re probably getting enough sleep on a regular basis.

Michael Scullin

Assistant Professor, Psychology and Neuroscience and Director, Sleep Neuroscience and Cognition Laboratory, Baylor University

If you’re a healthy human being, then, no, you should not be concerned about sleeping too much. Let’s say that you’ve just slept for ten hours straight, and you wake up feeling terrible—that’s usually not caused by sleeping too much, that’s usually caused by sleep-deprivation: you’ve built up a sleep debt over two or three days (or a week, or a month) of working hard or not taking care of yourself, and so finally on the night you do [get a lot of sleep] your brain decides it’s going to kick things into extra gear. It’s going to put you really deep in sleep, and it’s not going to let you wake up for 10 or 11 hours. In that situation, you’re probably waking up from a deeper stage of sleep than you normally would, because your brain’s trying to catch up on so much, and when we wake up from deep stages of sleep we just feel groggier.

The related issue is that if you’ve built up a big sleep debt—if you’ve been undersleeping for a long period of time—a single night of recovery’s just not gonna do it, and in fact, if anything, you’re going to wake up and your brain’s going be saying, “holy cow, you’re trying to get sleep again! I’ve been trying to get you to sleep for a while and you stopped doing it. Now that I see that you might actually sleep, I’m gonna make you feel extra sleepy in the morning, in the hopes that you’ll repeat that good sleep habit again today, or later that night.” There’s just not a compelling body of research that suggests that oversleeping can hurt healthy adults.

The counterpoint is that there are some conditions in which people sleep a really long time. Narcolepsy is one, and it’s related to a condition called hypersomnia, which is where people might sleep for upwards of 16 hours a day and still feel sleepy. They’re never able to satisfy that sleep debt.

Individuals who find themselves sleeping more than ten or eleven hours a night, night after night, every single night, and never feeling refreshed: Oh my gosh, go see a physician! Go see a sleep specialist as soon as you possibly can, because you very well could have a clinical condition that’s treatable.

The third component is people who are older, in their seventies or eighties. There’s all this epidemiological evidence—meaning population-based, questionnaire-based research—that shows that older adults who report sleeping longer than, let’s say, 10 or more hours a night, or 10 hours across a 24-hour cycle, are at higher risk for all sorts of health problems, including increased mortality risk. And there is data that shows an association between sleeping a lot when you’re older and higher risk of dying. But that’s probably getting away from the point that if you’re healthy, and you oversleep, it is probably not oversleeping. It’s prob just catching up on sleep. If you’re an older adult, and you’re really sleepy, and you’ve taken several naps during the day and you’re sleeping a long time at night, that can often indicate that there’s some underlying path, some underlying medical condition. But if anything sleep is probably trying to help you with whatever that underlying path is, and so it’s a symptom of that, rather than a cause of negative health outcomes.

Kevin Morgan

Professor, Clinical Sleep Research Unit, Loughborough University

This is a good question, but since it presumes the existence of an optimal sleep value, it’s worth first considering how much sleep is enough sleep. Importantly, the answer to this question is not a duration, it’s an experience. Most adults (over 70%) sleep somewhere between 6.5 to 8.5 hours per night. And many of those whose typical sleep duration falls outside of this range could be considered ‘normal.’ A better guide to sleep adequacy is how it makes you feel. Sleep which typically leaves you feeling reasonably refreshed, alert and able to keep going for most of the following day can be considered adequate. Because sleep delivers a survival advantage, natural selection spent millions of years refining this subjective experience of sleep adequacy. We should trust the results.

Within the biological economy of the circadian rhythm, then, ‘too much sleep’ is simply any value or quantum greater than ‘adequate.’ But this is unsatisfactory since it begs another question – what’s so bad about too much sleep (i.e. why is more than adequate “too much”)? Taking a broad bio-psycho-social perspective, there are a bunch of reasons why sleeping longer than you need to can have a downside: it can make you late for work, it places you out of sync with your family and friends, it encroaches on your wake-time and reduces opportunities for health-promoting physical activity (and in addition, increases your time spent unhealthily static); it attracts opprobrium which can degrade your mood and self-esteem; it messes with your appetite hormones, destabilizing your experience of hunger and satiety—and last, but by no means least, because one of the most robust findings in longitudinal sleep epidemiology is that those who report the longest typical sleep durations (say, 10 hours+/night) also tend to die significantly earlier than those who report ‘average’ sleep durations.

Rebecca Robbins

Postdoctoral Fellow, NYU School of Medicine and co-author of Sleep for Success! Everything You Must Know About Sleep But are Too Tired to Ask

We don’t really have consensus [in the sleep research community]. There’s consensus around how much is not enough—we know the consequences of insufficient sleep all too well. When you wake up after four hours of sleep, you’re much more likely to be irritable, or anxious, or simply out of sorts. And we do find that insufficient sleep over time chronically is associated with serious health outcomes. We generally recommend at least seven hours for adults.

In terms of longer sleep, some of the literature has found an association between long sleep and health risks—higher mortality rates, chronic disease. But the critique of that literature is that much of the research has been done with chronically ill populations—a group suffering from a chronic condition would require more sleep than average. All by way of saying that the jury’s still out on long sleep—and recommending more sleep can make someone think it’s ok to sleep in on the weekends, or bank sleep, or make up for lost sleep, when unfortunately good sleep is really all about consistency and habit.

Kenneth P. Wright

Professor, Integrative Physiology and Director, Sleep and Chronobiology Laboratory, University of Colorado Boulder

Currently, there is no good experimental evidence that shows that if we give healthy adults the opportunity to sleep longer there are negative outcomes, whereas there is extensive experimental evidence to show that if adults sleep less than 6-7 hours per night (there are likely individual differences) there are negative outcomes for cognition and metabolic health, for example.

There is evidence from the epidemiological research literature that shows associations between sleeping less than seven or greater than nine or ten hours per night and health problems in adults (again there are likely individual differences). It is possible that adults who sleep more than 9-10 hours per night already have some health problem (e.g., heart disease, depression) and such health problems could be one reason why they sleep more than is typical.

To my knowledge, at this time there are no experimental research studies that systematically provided longer sleep to adults and showed that more sleep alters physiology in a way that would increase the risk for health problems.

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