Sleeping more than 8 hours a night could increase risk of death: study

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New U.K. research has found that sleeping longer than the recommended amount could be bad for your health. More than eight hours of shut-eye is associated with an increased risk of cardiovascular disease and death, compared to sleeping less than seven hours.

Led by researchers from Keele University, along with colleagues at the University of Manchester, the University of Leeds and the University of East Anglia, the new analysis looked at 74 studies which investigated the link between sleep duration and sleep quality and the risk of mortality and cardiovascular disease.

Together, the studies included 3,340,684 participants who self-reported their sleep duration.

The researchers found that participants who reported sleeping for more than eight hours a night had a greater mortality and cardiovascular risk than those who slept for less than seven hours.

A sleep duration of ten hours a night was linked with a 30 percent increased risk of dying compared to sleeping for seven hours, a 56 percent increased risk of dying from a stroke and a 49 percent increased risk of dying from cardiovascular disease.

In addition, poor-quality sleep was associated with a 44 percent increase in coronary heart disease.

"Sleep affects everyone. The amount and quality of our sleep is complex," said Chun Shing Kwok, the study's lead researcher. "There are cultural, social, psychological, behavioural, pathophysiological and environmental influences on our sleep such as the need to care for children or family members, irregular working shift patterns, physical or mental illness, and the 24-hour availability of commodities in modern society.

"This research began because we were interested to know if it was more harmful to sleep below or beyond the recommended sleep duration of seven to eight hours. We further wanted to know how incremental deviation from recommended sleep duration altered risk of mortality and cardiovascular risk.

"Our study has an important public health impact in that it shows that excessive sleep is a marker of elevated cardiovascular risk.

"Our findings have important implications as clinicians should have greater consideration for exploring sleep duration and quality during consultations. If excessive sleep patterns are found, particularly prolonged durations of eight hours or more, then clinicians should consider screening for adverse cardiovascular risk factors and obstructive sleep apnea, which is a serious sleep disorder that occurs when a person's breathing is interrupted during sleep."

The results were published in the Journal of the American Heart Association.