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.
Seven to nine hours of sleep is the normal and healthy amount of sleep 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:
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.
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.
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.
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.
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.
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.
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.
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