Can You Oversleep? (And What it May Be Telling You About Your Health)

Key Takeaways:

• It is possible to oversleep. Sleeping more than 9 or 10 hours per night is correlated with an increased risk in cognitive impairment, heart disease, exhaustion, and other unwanted outcomes.
• Sleep and aging have a complicated relationship. Quality sleep is essential to healthy aging, yet oversleeping may be tied to the end-of-life process. 
• If you’re sleeping more than 10 hours per night, see your doctor. It could be a sign of a sleep disorder or other disease.

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When actress Dakota Johnson declared she sleeps up to 14 hours a night in a recent interview, the revelation created quite the buzz. Catching that many ZZZs may sound, well, dreamy to some, but science tells us that Johnson may be oversleeping, making her what is called a “long sleeper.” That’s a habit that correlates with certain health concerns you may want on your radar. 

Definition of oversleeping

The amount of sleep you need changes throughout your life, and can be impacted by activity level, lifestyle, and even your age, meaning what constitutes oversleeping may vary throughout your life. However, you are considered to be a long sleeper if you’re an adult who regularly sleeps more than a certain amount of hours per night. Some studies set this number at 9 hours, while the International Classification of Sleep Disorders - Third Edition puts it at 10. 

But notice that the word “regularly” is key here. If you have the occasional ultra-long slumber secession when you’re sick or in recovery mode from a procedure, that doesn’t qualify. But if it’s a regular occurrence, you’re a long sleeper.

Is oversleeping dangerous? 

While the benefits of getting enough sleep have been well-documented, there’s reason to believe that getting too much of it isn’t ideal. Several risk factors go up as the number of hours typically slept skews toward the long end. 

However, that isn’t to say that sleeping for long periods is in itself dangerous. It could be that excessive sleeping is merely an indicator of an underlying health condition. After all, a 2021 review of two human studies in which subjects were given the opportunity to extend their sleep time to 14 to 15 hours per day found no evidence that healthy people sustain long sleep over multiple days. This suggests that sleeping more than 10 hours could be a sign of a sleep disorder or other disease. 

The risk factors that increase with oversleeping

One factor commonly associated with oversleeping is still up for debate—obesity, for example. Some studies found an association between high body mass index scores and long sleep (2014 study in PLoS One). However, another study done just the year before found no correlation at all. But there are a few things research is a bit clearer on—though, again, we don’t know if oversleeping causes these conditions or if oversleeping is a symptom associated with them.

• Cognitive impairment. In a worldwide study featuring 40,000 people who did a series of cognitive performance activities and answered an in-depth questionnaire, those who slept more than eight hours performed worse cognitively than those who slept seven to eight.
• Diabetes. While not sleeping enough has been associated with diabetes, so too, is oversleeping. An analysis of over 56,500 subjects by the US National Health Survey found a link between regularly sleeping more than eight hours and this chronic disease.
• Cardiovascular diseases. Oversleeping has been linked to heart problems, including hypertension. In fact, in a Nurses' Health Study of over 70,000 women, those who slept nine to 11 hours per night were 38% more likely to have coronary heart disease than those who slept just eight hours. 
• Higher mortality risk. The PLoS One review points out that sleeping for 10 hours per night is associated with an increased mortality risk of 20% to 30%. The reason behind this isn’t clear, but two suggestions are that long sleep sessions could be a sign of the end-of-life process and long sleepers are more likely to have cardiovascular disease and diabetes.
• Depression. In a review of responses from the National Health and Nutrition Examination Survey (NHANES) from 2009 to 2016, both under- and oversleeping is associated with depression. 
• Exhaustion. As the review in PLoS One highlights, sleeping more than 10 hours per night is associated with feeling sleepy with an increase in hypersomnia, meaning the inability to stay alert all day even after meeting the minimum suggested hours of sleep. 

The “right” amount of sleep

There’s no perfect answer to how much sleep any one person should get, and your number very likely can and will change throughout your life as your body clock changes and your activity levels rise or fall. While the general advice is to get about eight hours per night (which is the amount that a large 2018 sleep survey found was associated with highly functional cognitive behavior across all ages), recent advice has moved toward paying more attention to how you feel throughout the day rather than trying to hit a certain number. “Don’t obsess about the mythical eight hours of sleep,” says neuroscientist, sleep expert, and Elysium Scientific Advisory Board member, Russell Foster, Ph.D. “It’s an average.” If you’re not feeling well-rested, it may be a sign you’re not getting the right amount of sleep to maximize your performance—or your health. 

“Don’t obsess about the mythical eight hours of sleep. It’s an average.” 

- Russell Foster, Ph.D., Head of the Nuffield Laboratory of Opthalmology and the Sleep and Circadian Neuroscience Institute, Chair of Circadian Neuroscience at the University of Oxford, and Elysium Scientific Advisory Board member

How sleep is related to aging

Numerous studies highlight the importance of quality sleep in healthy aging, as sleep is essential to the body’s processes of regulation, restoration, and repair. However, sleeping more in your golden years can be a sign of health deterioration, especially as you near the end of your lifespan. Remember: the 2018 sleep survey in PLoS One suggested that oversleeping in old age may be associated with end-of-life processes along with the fatigue and inactivity that can come with it.

On the flip side, it’s quite common for elderly people to report problems getting enough sleep, with an estimated 50 percent reporting some form of insomnia in their later years. The National Institute on Aging, suggests this may be due in part to shifts in the body’s circadian rhythm, as older adults often both go to bed and wake up earlier than they did in their younger years. And the reasons for this could be anything from increased pain, to certain medications to even Alzheimer’s Disease. 

What to do if you’re oversleeping?

If you’re routinely oversleeping, according to the Mayo Clinic, it may be a good idea to make an appointment with your doctor to rule out any underlying problems. He or she may send you for a sleep study, in which you’ll be monitored by a medical team overnight. In the meantime, practicing good sleep hygiene can improve the quality of your snoozing time in general. Here are a few to-dos from the Sleep and Circadian Neuroscience Institute at the University of Oxford:

• Stay on schedule. Try to go to bed and wake up at the same time every day. This includes the weekends, as sleeping in impacts your natural body clock and can just delay sleep that night. This can also help train your “chronotype” (i.e. whether you’re a morning or night person) to match your lifestyle, which can make for overall better sleep. And if you happen to habitually wake up in the middle of the night? Some research, including findings in a 2017 study, suggests some people may have a bimodal chronotype, meaning they do best with two blocks of sleep rather than one long stretch.
• Get some morning light. Getting in a little time in the sun in the a.m. hours can help your body’s natural circadian rhythm. 
• Develop a wind-down bedtime routine. Think a pre-bed bath, light stretching or yoga, and dimming your lights.
• Turn off screens in the hours before bed. Emerging research suggests that the light from these devices may interrupt sleep, so it’s best to switch them off 30 minutes before bedtime.
• Set your thermostat to slightly cool. According to the Cleveland Clinic, the ideal temperature is 60 to 67° F. 
• Leading up to bedtime, avoid: large meals, alcohol, caffeine, and big conversations that may leave your mind “chattering.” 
• Limit naps. Grabbing a quick catnap may do more harm than good, as it can make falling asleep later harder. The advice from the University of Oxford: When the need strikes, keep naps around 20 minutes and take them earlier in the day rather than later when it’s more likely to push back your bedtime.