If you sleep 8 to 9 hours every night, you’re less likely to have heart problems later on.
Evidence from Studies
Supporting (3)
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This study found that sleeping 7 to 8 hours a night is best for heart health, but sleeping more than 8 hours might actually be bad for your heart — so the claim that 8–9 hours helps isn’t fully right, since 9 might be too much.
This study found that people who sleep 7 to 9 hours a night have lower heart disease risk than those who sleep less, and sleeping more than 9 hours isn’t worse — so sleeping 8 to 9 hours is likely safe and helpful for your heart.
Causal association between sleep duration, daytime napping, sleep disorders and ischemic heart disease: A systematic review and meta‑analysis of Mendelian randomization studies
This study found that people who sleep longer — especially more than 6 hours — have a lower risk of heart disease. So sleeping 8–9 hours, as the claim says, likely helps protect the heart.
Contradicting (1)
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The study says sleeping 6 to 9 hours is safest for your heart, but the claim says only 8 to 9 hours is good — that’s too narrow. Sleeping 6 or 7 hours was just as safe, so the claim is wrong.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.