Sleeping more than eight hours increases risk of death from heart disease and/or stroke.

In a study by Kwok et al published in the Journal of the American Heart Associationthe researchers found that sleeping more than eight hours a night may increase the risk of death from heart disease or stroke, while sleeping fewer than seven hours did not affect one’s likelihood of death.

The authors searched MEDLINE and EMBASE databases and identified seventy‐four studies that included 3,340,684 participants.  In those studies 242,240 deaths were reported among 2,564,029 participants. Self‐reported duration of sleep of more than 8 hours was associated with a moderate increased risk of all‐cause mortality, with risk ratio, 1.14 (1.05–1.25) for 9 hours, risk ratio, 1.30 (1.19–1.42) for 10 hours, and risk ratio, 1.47 (1.33–1.64) for 11 hours. No significant difference was identified for periods of self‐reported sleep of less than 7 hours, whereas similar patterns were observed for stroke and cardiovascular disease mortality. Subjective poor sleep quality was associated with coronary heart disease (risk ratio, 1.44; 95% confidence interval, 1.09–1.90), but no difference in mortality and other outcomes.

The authors concluded that divergence from the recommended 7 to 8 hours of sleep is associated with a higher risk of mortality and cardiovascular events.