You may have heard the common advice to get eight hours of sleep a night, and may even have seen those super productive types getting six a night, but that’s just not you.
Perhaps even after eight hours of shut-eye, you have to hit the snooze button on your alarm clock quite a few times until you feel ready to get out of bed.
And if you’re regularly sleeping for nine hours a night, you might be worrying about whether this sleep schedule will lead to any health problems.
It’s easy to see sleep as similar to eating, in that eating too much can negatively impact your physical health. But can sleeping too much really impact your wellness as well? Below, we dive into what science has to say on the matter.
Nine hours of sleep isn’t too much if that’s the amount of sleep you need, and there are a few reasons why you may need nine hours.
Your sleep need is the amount of sleep you need each night. One study suggests the average sleep need is 8 hours and 40 minutes, plus or minus 10 minutes or so, but a surprisingly large percentage — 13.5% — may need 9 hours or more sleep a night.
If you’re finding yourself asleep for nine hours, you may just be one of the 13.5%.
It may feel like you’ve drawn the short straw when it comes to sleep needs, but it’s determined by genetics, just like height and eye color, so it can’t be changed.
To feel and perform your best each day, you need to work on meeting your sleep need each night, even if that is nine hours.
To find out your individual sleep need, you can use the manual method of waking up without an alarm clock for at least a week. Or, for a more accurate measurement, you can turn to the RISE app. The app uses your phone use behavior and proprietary sleep-science-based models to calculate your unique sleep need.
You can learn more about how to work out how much sleep you need here.
RISE users on iOS 1.202 and above can click here to view their sleep need.
When you don’t meet your sleep need, you start building up sleep debt. This is the running total of how much sleep you owe your body over the last 14 nights.
You can pay back sleep debt, however, by taking naps or sleeping for longer at night, or essentially by oversleeping your sleep need. So, this may be the reason you’re sleeping for nine hours, especially if it’s a recent change.
Say your sleep need is 8 hours 30 minutes, but you’ve spent the last two weeks getting six hours of sleep a night. You’ll have built up quite a lot of sleep debt.
When you can, your body will take the chance to catch up on sleep and pay down some of this debt by sleeping for longer.
And the higher your sleep debt, the longer it will take to recover, so you may find yourself sleeping for nine hours a night for several nights as your body has the urge to sleep more than usual to catch up.
RISE can work out how much sleep debt you have each night. While having no sleep debt is a great goal, it’s often unrealistic. So, we recommend keeping sleep debt below five hours to feel and function your best each day.
If your sleep debt is high, and your sleep need is below nine hours, this may be the reason you’re sleeping more.
RISE users on iOS 1.202 and above can click here to view their sleep debt.
You may also sleep more than usual after intense physical activity — runners who completed a 92-kilometer race slept significantly more than usual in the four nights following the race. They got much more sleep in general and more deep sleep than usual, probably because their bodies needed it to recover.
In some cases, medical conditions can be the reason people sleep for long durations.
For example, hypersomnia is a sleep disorder that affects 4% to 6% of the population, and it comes in many forms. Idiopathic hypersomnia causes people to sleep for abnormally long durations and still feel sleepy during the day, and recurrent hypersomnia causes people to sleep for 18 hours a day for a period of a few nights or weeks.
Mental health issues like depression or seasonal affective disorder (SAD) can also cause people to sleep more than usual. In fact, 80% of those with SAD say they suffer from hypersomnia. And when people not affected by SAD were surveyed, nearly half said they slept for two or more hours during the fall and winter months compared to the summer.
Speak to a healthcare professional if you think something like a sleep disorder or depression is the cause of you sleeping for nine hours or more.
If you get into bed at midnight and don’t get out again until 9 a.m., that doesn’t mean you’ve had nine hours of sleep. You most likely spent some of that time awake, and that’s where sleep efficiency comes in.
Sleep efficiency is the measure of how long you spend in bed actually sleeping. It combines sleep latency (how long it takes you to fall asleep) and sleep fragmentation (how much you wake up during the night) and it’s often converted into a percentage.
So, if you spent nine hours in bed, but only slept for seven of those, your sleep efficiency would be 77% (7 / 9 = 0.77 x 100 = 77%).
Bonus tip: Anything above 85% is considered good sleep efficiency, though you want to be aiming for 90%. But keeping your sleep debt low is much more important than sleep efficiency when it comes to your health and energy levels.
We all know we should be getting enough sleep. And getting too little sleep can lead to an increased risk of everything from obesity to diabetes, heart disease to cancer. But can getting too much sleep be harmful, too?
Some studies found sleep duration has what researchers call a “u-shape” association with adverse health effects. That means sleeping too little and too much may be bad for your health.
But studies often don’t relate to the general population. For example, one study found both short and long durations of sleep were associated with all-cause mortality. Short duration was described as less than seven hours, while long duration was more than nine hours, and seven to nine hours was deemed optimal. But the study was on those aged over 80, and studies on older adults may not apply to younger people.
In another example, a 2020 study found sleeping for nine hours or more a night was associated with lower self-rated health. But the key word here is “self-rated.” And these participants’ poor health could easily be down to their diet or other lifestyle factors and have nothing to do with their sleep.
Relatedly, many studies rely on self-reported data, including and especially sleep data. For example, research shows both short and long sleep durations may cause weight gain. But this conclusion relies on participants estimating their own sleep times, and as we’ve shown, it’s hard to know how long you’ve slept for each night when you take into account sleep efficiency.
Self-reported sleep data may actually be very inaccurate. For example, one study measured participants' sleep through both self-reported sleep logs and non-invasive sleep monitors. The results showed variation between the two methods across many sleep metrics, including sleep latency, sleep onset, sleep offset, number of nighttime awakenings, and duration of night awakenings (as well as number and duration of naps).
One paper noted some of the problems with studies linking long sleep durations to adverse health outcomes. It highlights:
Oversleeping has been linked to things like obesity, cardiovascular disease, and even death. But, before you panic, this relationship is often down to correlation, not causation. So, sleeping for long periods of time may not be the trigger of these things. Instead, it may be a sign of an underlying condition.
One paper on the topic concluded: “What is clear from the literature is that long sleep duration cannot be assessed as a risk factor, or independent causal factor, for mortality without also assessing the potential confounding impact of other health conditions such as depression, sleep apnea, and other physical comorbidities and behaviors (e.g., alcohol consumption) that, through various mechanisms, may manifest themselves through extended sleep duration.”
The authors also added: “The bulk of the literature supports that habitually long sleep duration is likely to be an indicator of poor physical and mental health status, but offers only weak evidence that extension of sleep, as an optional or directly modifiable behavior, is a driving causal force in patterns of mortality.”
And it all comes down to a common conclusion that more research needs to be done. A joint statement from the American Academy of Sleep Medicine and Sleep Research Society says: “Sleeping for more than 9 hours per night on a regular basis may be appropriate for young adults, individuals recovering from sleep debt, and individuals with illnesses. For others, it is uncertain whether sleeping more than 9 hours per night is associated with health risk.”
Nine hours of sleep a night only sounds like a lot because it’s on the upper end of the National Sleep Foundation’s recommended seven to nine hours of sleep a night for adults. But that recommendation is a generalization. It doesn’t take into account everyone’s individual sleep needs.
Plus, we live in a society where less sleep is often praised, and getting nine hours a night may make you feel unproductive and lazy. But, if that’s what your body needs, it’ll actually help you get more energy, better health, and be more productive in the long run.
And research suggests you may not even be able to sleep too much. A 2021 paper looked at two studies, one where participants were given the chance to sleep for 14 hours a night and another where they could sleep for 16 hours (12 hours at night and four hours during the day). However, both studies showed that once participants had caught up on sleep debt, they didn’t need that extra sleep. In fact, no individual consistently slept for more than 10 hours.
The researchers concluded: “In response to the question: “Can I sleep too much?,” the answer is “No,” since “too much” implies sleeping longer than is biologically necessary.”
They added people cannot oversleep in the same way they can overeat and said no causal links have been found between oversleeping and adverse health effects, whereas there are plenty of links between undersleeping and adverse effects.
If you’re getting enough sleep each night and still feeling sleepy all the time, this doesn’t necessarily mean you need nine hours of sleep or more (although, that’s definitely a possibility — use RISE to find out what your sleep need is).
There are a few reasons why you may be meeting your sleep need and still feeling tired.
You may be feeling tired, even if you’re getting enough sleep, due to:
You can check RISE to see how long morning grogginess is expected to last and when your afternoon dip in energy is expected to be each day.
We cover more reasons why you’re always tired here, and what you can do about it — the solution isn’t always to sleep for nine hours or more.
You should speak to a doctor if you’re regularly experiencing excessive sleepiness despite meeting your sleep need.
It can feel almost impossible to know if you’re sleeping too much. We all need a different amount of sleep and many factors may make us sleep more than usual.
Take the guesswork out of it by turning to the RISE app to find out your sleep need down to the minute. The app can also automatically track your sleep times, so you can see if you overshoot your sleep need regularly.
But remember, if you have sleep debt, your body will want to sleep for longer than your sleep need as it pays this back.
So, as well as knowing your sleep need, you also need to keep an eye on your sleep debt. RISE works this out each day, so you can see how much you have.
Sleeping for nine hours every now and again, if this is more than your sleep need, isn’t a problem. It could simply be your body needing some extra rest due to intense exercise or an illness. But you should speak to a doctor if you’re worried about massively oversleeping your sleep need on a regular basis.
You can learn more about how much sleep you need here.
Nine hours of sleep may sound like a lot, but that may be exactly what your body needs to reach your full potential. Use the RISE app to find out your individual sleep need.
If it’s nine hours, work to get this amount each night to maximize your energy levels the next day and long term. And if your sleep need is lower, check on your sleep debt to see if your body is simply catching up on lost sleep.
You should speak to a doctor if you think a medical condition or sleep disorder is the reason you’re sleeping for nine hours or more a night. But remember, it is hard for your body to “oversleep” and there are many other factors that may be causing daytime sleepiness.
It is OK to sleep 9 hours a night if your sleep need — the genetically determined amount of sleep your body needs — is this amount. It’s also OK if your sleep need is less, but you’ve got high sleep debt, so your body is getting more sleep than usual because of recent sleep deprivation.
You might sleep 9 to 10 hours a night if your sleep need is this amount or if you have high sleep debt and your body is catching up on lost sleep. You may also sleep 9 to 10 hours a night if you’re recovering from an illness or from intense exercise, or if you have a medical condition like hypersomnia.
10 hours of sleep isn’t too much if your sleep need is this high or if you’ve got high sleep debt and you need to make up for a lack of sleep in recent nights. You may also sleep for longer if you’re ill or after intense exercise. If your sleep need is lower than 10 hours and your sleep debt is low, speak to a doctor about underlying medical conditions that could be causing you to sleep for this long.
Sleeping for 9 hours can make you tired if you’ve slept in and woken up during a dip in your circadian rhythm or woken up halfway through a sleep cycle while in deep sleep. Even if you need 9 hours of sleep a night, you may feel tired because of sleep inertia, circadian misalignment, or pre-existing sleep debt.
It’s hard to say how much sleep is too much as everyone has a unique sleep need — the genetically determined amount of sleep their body needs. You may oversleep your sleep need if you have sleep debt, you’re ill, after intense exercise, or because of an underlying medical condition.
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