Most adults need 7-9 hours of sleep per night. The National Sleep Foundation's guidance is 7-9 hours for adults aged 18-64 and 7-8 hours for adults 65 and older. In June 2022 the American Heart Association added sleep duration to its cardiovascular health score — Life's Essential 8 — using the same 7-9 hour range for adults, on the basis that inadequate sleep independently raises the risk of heart disease, stroke, hypertension, obesity, diabetes and premature death. At the short end, a 2011 meta-analysis in the European Heart Journal (15 studies, more than 470,000 participants) found that consistently sleeping fewer than 6 hours was associated with a 48% higher risk of developing or dying from coronary heart disease, compared with 7-8 hours.
Recommended hours by age
The National Sleep Foundation's recommended ranges, which the American Heart Association aligns with for adults in Life's Essential 8:
| Age group | Recommended sleep per night |
|---|---|
| Adults 18-64 | 7-9 hours |
| Adults 65 and older | 7-8 hours |
These are ranges, not pass/fail lines. The foundation notes that the right amount is the one that leaves you waking refreshed, and that consistent sleep and wake times matter alongside total hours.
Why the AHA made sleep a cardiovascular metric
For more than a decade the AHA measured cardiovascular health through seven factors — physical activity, diet, weight, smoking status, blood pressure, cholesterol and blood glucose. In June 2022 a presidential advisory published in Circulation added sleep duration as the eighth, renaming the score Life's Essential 8. The change reflected accumulated evidence that sleep is a biological requirement with direct cardiovascular consequences, not a lifestyle preference.
The practical implication: sleep is now assessed alongside blood pressure and activity when clinicians think about cardiovascular risk — which is why a watch that shows your sleep duration is showing something with standing behind it.
What short sleep is associated with
A 2011 systematic review and meta-analysis by Cappuccio and colleagues, published in the European Heart Journal, pooled 15 studies covering more than 470,000 participants. Compared with sleeping 7-8 hours, consistently sleeping fewer than 6 hours was associated with a 48% higher risk of developing or dying from coronary heart disease, and a higher risk of stroke.
Separately, the US Centers for Disease Control and Prevention estimates that about 1 in 3 American adults do not get the recommended amount of sleep. Short sleep has been linked to higher inflammatory markers, impaired glucose metabolism and endothelial dysfunction — all of which feed into cardiovascular risk.
More is not always better
The relationship between sleep duration and cardiovascular risk is U-shaped: risk is higher at both the short and the long end. Consistently sleeping around 10 hours or more is also associated with elevated risk, though researchers caution this often reflects underlying illness or depression rather than long sleep itself being harmful.
Duration is also only part of the picture. Someone who spends eight hours in bed with untreated sleep apnoea, or with fragmented sleep, may get little restorative slow-wave sleep — the total can look adequate while the recovery does not happen.