Oversleeping: The Effects and Health Risks of Sleeping Too Much

We often hear about the real dangers of getting too little sleep, but on the other end of the spectrum, sleeping too much also appears to have some risks.

Sleep is a rapidly growing field of research, and we are learning more all the time about how rest affects the body and mind. It's known that sleep is a time when the body repairs and restores itself, and getting too little rest can lead to a whole host of health problems.

So, more sleep must be better right? Not so fast, say some researchers.

More evidence is showing that spending an excess amount of time in bed is also linked with health hazards. In some ways, oversleeping itself appears to directly influence certain risk factors, and in other cases, it may be a symptom of other medical conditions.

Read on to learn about the effects of oversleeping, what to look out for and how to work towards getting healthy, quality slumber.


Are You Sleeping Too Much?

First, let's address what oversleeping means. The gold standard of normal has long been considered eight hours, and it's a good median benchmark. Recent reviews of current research from the experts at the National Sleep Foundation broaden the spectrum a little. They say that somewhere in the range of seven to nine hours is normal and healthy for most adults between 18 and 64 years of age.

        

Some say closer to seven hours could be even better, such as Arizona State University professor Shawn Youngstedt, who told the Wall Street Journal, "The lowest mortality and morbidity is with seven hours." Other researchers have also linked seven hours of rest with things like longevity and better brain health.

The "right" amount of sleep proves somewhat individual as some people will feel great on seven hours and others may need a little longer. However, in most studies and for most experts, over nine hours is considered an excessive or long amount of sleep for adults.

If you sleep in a little sometimes on the weekends, it's likely no big deal. If you regularly sleep more than nine hours each night or don't feel well-rested on less than that, then it may be worth taking a closer look. It's estimated that about 2% of the population are naturally long sleepers (typically since childhood), but long sleep can also coincide with health issues and other treatable factors.


The Health Impact of Oversleeping

Seeking to find the sleep "sweet spot" for optimal health, researchers have been busy recently looking at how different habits connect with physical and mental well-being. Several trends have emerged linking oversleeping with higher rates of mortality and disease as well as things like depression.

Research Links Longer Sleep Habits with:
Cognitive impairment
Depression
Increased inflammation
Increased pain
Impaired fertility
Higher risk of obesity
Higher risk of diabetes
Higher risk of heart disease
Higher risk of stroke
Higher all-cause mortality

Impaired Brain Functioning and Mental Health

Sleep plays an important role in the brain, as the brain clears out waste byproducts, balances neurotransmitters and processes memories at rest. At both short and long extremes, rest may have an effect on mood and mental health.

Cognition
Using data from the Lumosity brain-training platform, researchers found that cognitive performance on three different games all peaked when people slept around seven hours, worsening with more or less rest. Other studies have also found memory impairments and decreased cognitive function with longer sleep.

Degenerative Diseases
Other research indicates that getting too little or too much sleep may be tied to increased Alzheimer's disease risk factors and a large Spanish study found that long sleepers may be at increased risk of developing dementia.

Depression and Mental Health
Oversleeping is considered a potential symptom of depression. While many people with depression report insomnia, about 15% tend to oversleep.

People with long sleep durations are also more likely to have persistent depression or anxiety symptoms compared to normal sleepers. A recent twin study also found that sleeping too little or too much seemed to increase genetic heritability of depressive symptoms compared to normal sleepers.

A study of older adults also found that those who slept more than 10 hours reported worse overall mental health over the past month compared to normal sleepers.

Some research shows that irregularities in the body's sleep clock may play a role in depressive symptoms, and returning sleep to a healthy pattern is often a focus of treatment.


Increased Inflammation Factors

Chronic inflammation in the body is tied with increased risk of everything from diabetes to heart disease to Alzheimer's disease. Certain lifestyle factors like smoking, being obese, and prolonged infections can contribute to inflammation, and getting too little or too much sleep may also play a role.

Inflammation in the body is measured by levels of cytokines (also called C-reactive proteins, or CRP). One study compared CRP levels and sleep durations in a large group of adults, finding that male and female long sleepers had elevated levels.

Some differences were seen among races in the study though, suggesting sleep duration may not be one-size-fits-all. Elevated CRP was seen in:

Whites sleeping less than five and more than nine hours.
Hispanics/latinos sleeping more than nine hours.
African-Americans sleeping less than five and eight hours.
Asians sleeping more than nine hours. Interestingly, Asians sleeping five to six hours had the lowest levels, a pattern mimicked in another Taiwanese study.

Two previous studies also found links between inflammation and longer sleep. One showed that female long sleepers had 44% higher CRP levels compared to women sleeping seven hours. Another found that CRP levels increased by 8% for each additional hour of sleep beyond the norm (7-8 hours), adjusting for factors like body mass, age and sleep apnea.

Increased Pain
While many times it can seem intuitive to rest more when we're in pain, research shows that in some cases too much sleep can exacerbate symptoms.

Back pain can worsen from too little activity or spending too much time in bed. Sleeping in an un-ergonomic position or using an old or unsupportive mattress can also worsen back pain. Combined with staying still for a long period of time, these factors mean many people awake with worse back pain especially when spending longer amounts of time in bed.

Oversleeping is also linked with higher rates of headaches. Referred to as a "weekend headache," sleeping in may trigger migraines and tension headaches. The cause isn't necessarily sleep itself, though, as some researchers link it with caffeine withdrawal or increased stress.

Impaired Fertility
A study of Korean women undergoing in vitro fertilization therapy found that women who slept seven to eight hours had the best chances of conceiving. The moderate sleepers had the highest pregnancy rates (53%) compared to those sleeping six hours or less (46%) and those sleeping nine to eleven hours (43%). Study authors suggest sleep outside the normal range could be affecting hormones and circadian cycles, impairing fertility.

Impaired Glucose Tolerance
Glucose tolerance refers to the body's ability to process sugars, and impaired glucose tolerance is a associated with insulin resistance and is a risk factor for type 2 diabetes and heart disease.

A Canadian study looked at lifestyle habits of 276 people over six years, finding that people with long and short sleep durations were more likely to develop impaired glucose tolerance and diabetes during the timespan compared to normal sleepers (20% versus 7%). A recent review of diabetes and sleep studies found consistent relationships between increased risks of type 2 diabetes and both short and long sleep as well.

Increased Weight Gain
Using the same data as the previous six-year Canadian study, researchers also found links between weight gain and sleep. Short and long sleepers both gained more weight than normal sleepers over the six year period (1.98 kg and 1.58 kg), and were more likely to experience a significant weight gain. People sleeping over nine hours were 21% more likely than normal sleepers to become obese during the study.

Other studies generally only support trends of higher body weight for short sleepers, but it could be that associated factors like diabetes risk contribute to weight gain for long sleepers.

Higher Heart Disease Risk
Using information from the large National Health and Nutrition Examination Survey (NAHNES), researchers linked both short and long sleep with higher risk of coronary heart disease and stroke. The study found that people sleeping more than eight hours per night were twice as likely to have angina (chest pain caused by reduced blood flow) and 10% more likely to have coronary heart disease.

Analysis of the data from the Nurses' Health Study, which involved over 71,000 middle-aged women, also found connections between sleep length and heart health. Compared to normal eight hour sleepers, women sleeping nine to 11 hours per night were 38% more likely to have coronary heart disease.

Higher Stroke Risk
A recent study from University of Cambridge researchers looked at data from around 9700 Europeans over a period of 11 years. People who slept over eight hours were 46% more likely to have had a stroke during the study period after adjusting for comorbid factors. People whose sleep duration had increased during the study had a four times higher risk of stroke than consistent sleepers, suggesting that longer sleep could be an important symptom or warning sign of stroke risk.

Data from older NHANES surveys also found a significant relationship was found between long sleep and stroke risk. People who slept more than eight hours had a 50% higher risk of stroke than people who slept six to eight hours. People who slept over eight hours and who also had daytime drowsiness had a 90% higher stroke risk compared to normal sleepers.


Higher All-Cause Mortality Risk
In addition to (and perhaps as a result of) all of the other associated health issues like obesity, heart disease and stroke, longer-than-normal sleeping is also linked with higher risk of death in general.

In data from the second Nurse's Health Study, researchers sought to see what types of habits of lifestyle factors showed the strongest relationships between long sleep and increased mortality risk. It's suggested that several things might contribute to the higher risk of death, but based on their statistical analysis, the strongest influential factors were identified as depression and low socioeconomic status. In the Nurses' Study data, long sleep was also associated with numerous other conditions from obesity to multiple sclerosis to asthma to depression and antidepressant use.

To further get an idea of why people who sleep longer tend to have higher rates of death in long-term studies, clinical psychologist and sleep specialist Dr. Michael Grandner led aliterature review that identifies a few potential causes:


Sleep fragmentation: More time in bed is linked with more frequent wakings after sleep and reduced sleep efficiency (more time spent awake in bed).
Fatigue: Fatigue and lethargy can cause longer sleep, and sleeping longer can make people feel more lethargic.
Immune function: Longer sleep can influence expression of cytokines.
Photoperiodic abnormalities: Spending a long time in the darker rooms could affect the circadian cycle.
Lack of challenge: Spending a lot of time in bed may give less time for beneficial challenges (such as exercise).
Underlying disease: Obstructive sleep apnea, depression, coronary disease, and generally failing health.

The Chicken and Egg Dilemma
Looking at the information on the effects of oversleeping, the question of "which came first" is a fairly prominent one for researchers. Does oversleeping itself harm health, or do certain illnesses cause oversleeping?

Whether or not long sleep is the cause or the effect is often not immediately discernible with the data that looks at large groups of people and self-reported habits, however. Some studies indicate getting too much sleep or being overly sedentary may trigger certain problems, while other times the desire for more rest it could a byproduct of co-occurring processes.

Some researchers also highlight that the healthiest people may just need less rest while unhealthy people tend to need more due to known or undiagnosed problems. One way to test the idea of cause and effect for some of the shorter term conditions are controlled studies in which normal sleepers rest for longer hours and changes are observed.

A review of controlled studies on extended sleep finds that when adults sleep longer than normal, they tend to report increased fatigue, irritability and lethargy -- possibly triggering the desire to sleep more and perpetuating a cycle. Also reported are lower mood, slower reaction time, poorer math performance and more fragmented sleep, which has several health implications as well.

Other research of young adults showed that spending an additional two hours in bed each night over three weeks resulted in participants feeling more depressed, reporting more soreness and back pain, and they also showed elevated inflammation markers.


Setting the Stage for Healthier Sleep

The field of sleep science is still looking into the cause and effect relationship between oversleeping and health, but some habits and steps that promote better quality sleep and a healthy sleep duration are known.

While a small percentage of people naturally sleep longer, for many long sleepers (especially whose sleep needs have changed), there are certain conditions, behaviors and environmental factors that can increase sleep need or affect sleep quality (making you feel less rested on a normal amount).

To get an idea of how to avoid oversleeping and get healthier Zzz's, we reached out a few sleep experts for their words of wisdom. Here's what they had to say:



Dr. Robert Rosenberg


Too much sleep on a regular basis can increase the risk of diabetes, heart disease, stroke and death according to several studies done over the years. Too much is defined as greater than nine hours.

The most common cause is not getting enough sleep the night before, or cumulatively during the week. This is followed by sleep disorders such as sleep apnea, idiopathic hypersomnolence, as well as depression.

Get enough sleep, seven to nine hours a night.
Do not oversleep on weekends this throws your circadian rhythms off and makes falling asleep even more difficult when the work week comes along.

Expose yourself to bright sunlight upon awakening. Consider leaving the drapes or blinds open at night. That morning sunlight will help you to wake up.

Consider getting a dawn sunlight emitting alarm clock. Many of my patients are using them. You can set the dawn light to start filling your room with light 15 to 30 minutes before the alarm goes off.

Avoid excessive naps especially after 4PM. These may make it more difficult to fall asleep and result in oversleeping. The same goes for excessive caffeine and blue light exposure close to bedtime.

There are myriad reasons to avoid oversleeping from loss of your job to missing out on mornings with your family. However if you continue to have this problem and struggle to wake up make sure there is not an underlying sleep disorder at fault.