Is Too Much Sleep Bad For You? The 7 Side Effects Of Oversleeping


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The message about the importance of sleep is unavoidable to the extent that it seems like it is drilled into us all the time in various ways. 

There are commercials on TV for sleep medications, the going advice always seems to be to get more sleep when you are not feeling well, and almost every health article provides at least one tip that has something to do with getting more sleep.

And it’s true: getting enough sleep is absolutely essential to feel your best and to optimize your health. Most health experts recommend that adults get between 7 to 9 hours of sleep per night.

But, is too much sleep bad for you? In other words, is it bad to sleep too much? And, what is “too much“? Is it possible to oversleep?

In this article, we will discuss oversleeping, both in terms of how it is defined, what it entails, risk factors and causes, and most importantly, we will aim to answer the question, “is too much sleep bad for you?”

We will look at: 

  • What Is Oversleeping?
  • Is It Bad To Sleep Too Much?
  • Is Too Much Sleep Bad For You?
  • Why Am I Sleeping So Much?

Let’s jump in!

A woman sleeping peacefully in bed.

What Is Oversleeping?

So, before we answer the question, “Is sleeping too much bad for you?“ we need to define what is “too much sleep.“

According to the Sleep Foundation, oversleeping, which refers to sleeping too much, is defined as sleeping for over nine hours a night or sleeping for more than nine hours in a 24-hour period.

Hypersomnia is a condition that is marked by oversleeping as well as sleepiness during the daytime. In other words, with hypersomnia, you may be getting more than nine hours of sleep at night, yet you still feel excessively tired during the day.

When you have hypersomnia, in addition to sleeping more than nine hours per night, you may experience other symptoms such as excessive daytime sleepiness, excessive napping or nodding off during the day, and headaches.

Narcolepsy is a condition that can cause hypersomnia, but there are other sleep disorders and health conditions that may also cause oversleeping and/or hypersomnia, including obesity, mononucleosis, fibromyalgia, and obstructive sleep apnea.

In cases where an underlying cause of oversleeping cannot be identified, it is termed idiopathic hypersomnia.

The words sleep disorder on a sign with a packet and bottle of pills next to it.

Is It Bad To Sleep Too Much?

There is an abundance of evidence to suggest that getting enough sleep, and getting high-quality sleep, is important for overall health, mental alertness, focus, mood regulation, and energy.

Although the recommended amount of sleep per night for adults falls within the 7-9 hour range, the exact amount of sleep that you personally need can depend on a variety of factors such as your age, lifestyle, diet, physical activity habits, and overall health.

Competitive athletes often need more sleep, and some people feel completely rested with only six hours of sleep per night.

Occasional oversleeping is totally normal and sometimes even ideal or healthy. 

For example, if you are sick or recovering from an illness, oversleeping, which again is defined as sleeping more than nine hours in a night, can help give your body the extra rest that it needs to recover. Or, perhaps you are rundown from traveling or have jet lag. 

In these certain situations, occasional oversleeping is not an issue. But in other situations, is oversleeping bad?

However, if you are habitually oversleeping, it may be indicative of an underlying health issue, a sleep disorder, or a mental health disorder. Furthermore, independent of any of these possible causes or risk factors for oversleeping, sleeping too much can be bad for you.

A man sleeping in bed.

Is Too Much Sleep Bad For You?

It’s likely rather counterintuitive that sleeping too much would be bad for your health. After all, we routinely hear about how crucial getting enough sleep is for your health. But is oversleeping bad for you in some cases?

However, studies have found that sleeping too much is associated with an increased risk of many diseases, including cardiovascular disease, obesity, and diabetes, as well as an increased risk of all-cause mortality.

In fact, the health risks associated with sleep display a U-shaped relationship such that getting too little sleep is associated with an increased risk of chronic diseases, and getting too much sleep is similarly associated with the same heightened risk. 

The sweet spot for optimal health and disease reduction is right in the middle, around that 7 to 9 hours per-night range.

Here are some of the evidence-based risks of sleeping too much:

A person in bed in the dark with an alarm clock.

#1: Impaired Cognitive Performance

Studies have found that cognitive performance is optimized when people sleep seven hours per night and decreases with more or less sleep.

Other studies have found a similar U-shaped association between sleep duration and cognitive performance, again suggesting that oversleeping can impair brain function, including memory.

#2: Increased Risk of Alzheimer’s Disease

Sleeping too much can increase the risk of Alzheimer’s disease and dementia in much the same way that sleeping too little can.

#3: Increased Pain

Pain is certainly a situation that can make us more prone to want to sleep. However, although perhaps counterintuitive, studies suggest that too much sleep may actually exacerbate pain.

For example, being sedentary in bed for too long can worsen back pain, particularly if your mattress is unsupportive or you are sleeping in a position that is not anatomically sound or ergonomic. Some studies have also found that oversleeping can potentially increase the risk of headaches or migraines. 

A person in bed, holding his neck in pain.

#4: Impaired Fertility

One study that looked at the successful pregnancy rate among women undergoing in vitro fertilization therapy found that sleeping too much decreased fertility rates.

Fertility was optimized when women slept between 7-8 hours per night. Pregnancy rates were 53% for this ‘normal sleep” duration. However, fertility rates dropped to 43% in those sleeping 9-11 hours per night.

The researchers hypothesized that sleeping too much disrupts the body’s circadian rhythms, which in turn, alters hormones and impairs fertility. 

#5: Increased Risk of Depression

The link between oversleeping and depression is somewhat akin to a chicken-or-egg scenario. 

Depression can lead to oversleeping (in that oversleeping can be a symptom of depression), but oversleeping can also increase the risk of depression and anxiety. 

#6: Increased Weight Gain

Sleeping too much may increase your risk of unwanted weight gain. 

Over a six-year study, people who slept more than nine hours per night were 21% more likely than those who slept 7-9 hours per night to become obese during the time course of the study. 

A person sitting up in bed with the comforter over her head.

#7: Impaired Blood Sugar Regulation

One of the risks of sleeping too much is that it can impair your body’s ability to regulate blood sugar.

For example, evidence suggests that sleeping too much can increase the risk of type 2 diabetes. 

Studies have also found that people who habitually sleep too much are at a higher risk of developing impaired glucose tolerance, metabolic syndrome, and type 2 diabetes compared to those who sleep between 7-8 hours per night. 

Glucose tolerance refers to how well your body can digest, absorb, and use sugars. Impaired glucose tolerance is considered a risk factor for insulin resistance, type 2 diabetes, and heart disease.

Researchers believe that sleeping too much may increase the risk of any of the aforementioned because it can disrupt circadian rhythms and depress immune function.

A person in bed with their arms over their face.

Why Am I Sleeping So Much?

So, what causes oversleeping? Why might you be sleeping too much?

There are various causes of oversleeping. With acute oversleeping, you might be sleeping more than nine hours per night in order to “catch up“ or make up for sleep debt. 

For example, if you had a couple of late nights or nights of poor sleep, you might be oversleeping as a way to make up for the rest and recovery you missed out on.

If you are sick or fighting often illness or recovering from an illness, you may be oversleeping because your body is feeling run down and trying to recuperate.

However, if you are habitually oversleeping, it is usually a sign of an underlying physical or mental health issue or a sleep disorder, such as the following:

A person sleeping in bed with an alarm clock, glasses and a book on their nightstand.
  • Sleep disorders, such as narcolepsy, insomnia, or obstructive sleep apnea
  • Depression and anxiety
  • Fibromyalgia or chronic pain
  • Hypothyroidism
  • Chronic infections or mono
  • Lyme disease
  • Diabetes

If you are chronically oversleeping, particularly if you do not know the underlying reason, it is important to speak with your healthcare provider for further evaluation. 

You may need a sleep study or testing to identify and address underlying issues.

What happens on the other end of the spectrum if you are working on too little sleep? Check out our article Running On No Sleep: The Effects Of Sleep-Deprived Workouts if this applies to you.

A person yawning.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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