11/05/2013 08:17 am ET Updated Jan 23, 2014

Can You Really Sleep Too Much? Really?

You may be aware that sleeping too little can increase your risk of serious and chronic health problems. But did you know that too much sleep can also boost your risk for disease?

In our 24/7 always connected society, when it seems that most people are struggling to get enough sleep, the problem of sleeping too much may not seem like much of a problem at all. Yet prolonged sleep is associated with many of the same health problems as insufficient sleep. New research shows that both sleeping too much and sleeping too little are linked to elevated risks of chronic disease in middle-aged adults.

A large-scale study conducted by the Centers for Disease Control found that both insufficient and prolonged sleep are associated with a range of serious and chronic conditions including diabetes and cardiovascular disease. The study included 54,269 men and women aged 45 years and older. All had participated in the CDC's Behavioral Risk Factor Surveillance System, an ongoing survey that collects health information at the state level. Respondents in this study came from 14 states around the U.S. For the purpose of their investigation, researchers defined too little sleep as six hours or less per night. Too much sleep was defined as 10 hours or more per night, and optimal sleep duration was in the range of seven to nine hours. They found "short sleep" was more common than "long sleep," but that both short and long sleep durations were linked to elevated risks of chronic disease:
  • Nearly one-third of respondents -- 31.1 percent -- reported sleeping six hours or fewer per night. The majority of respondents, 64.8 percent, reported sleeping in the optimal range of seven to nine hours.
  • Slightly more than four percent of adults reported sleeping 10 or more hours per night.
  • Both short sleep and long sleep were associated with greater risks of coronary heart disease and stroke.
  • Short sleep and long sleep were also associated with elevated risk of diabetes and obesity. Both short and long sleepers were significantly more likely to report frequent mental distress, defined by researchers as an experience of poor mental health on 14 or more of the previous 30 days.
  • Long sleepers had even higher risks of coronary heart disease, stroke and diabetes than short sleepers did.

As researchers themselves point out, the relationships between unhealthy sleep duration (too short and too long) and other factors such as mental health and body weight are complicated. The researchers suggest -- rightly so -- that more study is needed to understand how these factors of sleep, mental health, and weight interact with each other to influence risk of chronic disease.

The negative health effects of too much sleep are not as well known as the risks of not sleeping enough. Research shows that prolonged sleep duration can carry many of the same risks as insufficient sleep -- and sometimes the risks are even higher:

  • Insufficient sleep is a well-known risk factor for diabetes. A number of studies also show that sleeping too much increases the risk of diabetes and metabolic disorders, including metabolic syndrome. Some research suggests that long sleep poses similar levels of increased risk as short sleep, while other studies indicate the diabetes risk to long sleepers is even greater.
  • Cardiovascular problems, including high blood pressure and heart disease, are also linked to both insufficient sleep and prolonged sleep. An investigation that included data from the Nurses' Health Study on more than 71,000 women showed that long sleep duration was associated with increased risk of coronary heart disease. Research shows that abnormal sleep duration -- long or short -- may nearly double the risk of some cardiovascular disease.
  • Long sleep periods are associated with accelerated cognitive decline in older adults. Researchers at Spain's University Hospital Madrid and New York's Columbia University examined the possible impact of sleep duration on cognitive function in adults in their 60s and 70s. They observed 2,700 men and women in this age group over a period of three years during which time all types of sleepers -- short, normal and long -- experienced some degree of cognitive decline. Researchers found that those who regularly slept more than nine hours per night experienced much more significant decline in cognitive function, almost double that of normal sleepers. About 40 percent of the adults in this group were long sleepers.

There is still a great deal more to understand about how abnormal sleep duration, whether short or long, affects health. The more we learn about sleep and its relationship to health and disease, the more it appears that there is an optimal amount of sleep, in the range of seven to nine hours per night. The problem of getting enough sleep is markedly more common, and deserves all the attention it gets -- and more. That said, we ought not lose sight of the health hazards associated with sleeping too much.

Don't mistake sleeping more with sleeping better. For the best sleep for long-term health, aim for a not-too-little, not-too-much middle ground.

Sweet Dreams,
Michael J. Breus, PhD
The Sleep Doctor®

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