Causal association between sleep duration, daytime napping, sleep disorders and ischemic heart disease: A systematic review and meta‑analysis of Mendelian randomization studies

If you sleep 8 to 9 hours every night, you’re less likely to have heart problems later on.

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 take a lot of naps during the day might be more likely to develop heart problems, even if they sleep well at night and aren’t overweight—this could mean their sleep isn’t restful or their heart is under extra stress.

People who have trouble sleeping—like not being able to fall asleep, stopping breathing at night, or falling asleep at the wrong times—are much more likely to develop heart disease, and it might be because poor sleep messes up the body’s stress, inflammation, and metabolism systems.

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.