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For decades, scientists have examined how sleep patterns affect longevity. Early research in 1989 showed that chronic sleep deprivation in rats increased mortality, a finding that has since been confirmed in human studies. More recent evidence suggests that excessive sleep can carry similar dangers.
In a landmark study by University College London and the University of Warwick, researchers tracked over 10,300 participants at two points in their lives—between 1985‑88 and again in 1992‑93. After controlling for age, employment grade, alcohol use, and other variables, the team presented their findings to the British Sleep Society in 2007. They reported that sleeping eight hours or more doubled the risk of all‑cause mortality.
These findings were reinforced in a 2018 study by Keele University, published in the Journal of the American Heart Association. Analyzing data from more than 3 million adults, the researchers concluded that sleeping 10 hours or more per night increased overall mortality risk by 30% compared with a seven‑hour sleep schedule. They also found that participants who slept 10+ hours were 56% more likely to die from stroke and 49% more likely to die from cardiovascular disease.
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Oversleeping is defined as sleeping more than nine hours in a 24‑hour period. While sleep disorders such as apnea, insomnia, and narcolepsy are obvious culprits, a host of other conditions can drive excessive sleep. Anxiety, depression, cardiovascular disease, chronic pain, diabetes, and obesity are all linked to prolonged sleep. Chronic oversleeping can increase inflammation, contribute to chronic disease, and weaken the immune system. Fortunately, many of these conditions are treatable, making it easier to restore healthy sleep patterns.
The Centers for Disease Control and Prevention (CDC) recommends the following daily sleep durations based on age:
