People who sleep six hours or less each night are more likely to develop heart disease, and this might be because not enough sleep messes up their metabolism and causes body inflammation.

People who sleep less than 7 hours a night are more likely to develop heart problems like heart attacks or irregular heartbeats than those who sleep 7 to 9 hours.

If you usually sleep less than 6 hours a night and start getting 7 to 8 hours instead, you’re less likely to develop heart disease—so getting enough sleep might help keep your heart healthy.

Sleeping more than 9 hours a night doesn’t make your heart healthier—once you’re getting 7 to 8 hours, sleeping longer won’t lower your risk of heart disease.

People who say they sleep too little or too much are more likely to die from heart problems, but only those who actually sleep too little (measured by devices) show a clear link—so sleeping a lot might just mean you’re sick or your sleep is bad, not that you’re sleeping too much.

People who sleep too little or too much are more likely to die sooner, even if they don’t have severe sleep apnea — which suggests that how long you sleep might be harmful all on its own.