Sleep and Longevity: Why 7 Hours Is the Sweet Spot

The number: roughly 1 in 3 American adults are sleep-deprived

According to CDC National Health Interview Survey data, between 30% and 37% of U.S. adults report sleeping fewer than 7 hours on a typical night. The range shifts by age and race — adults aged 50–64 are among the most likely to be short sleepers, with 34.5% falling under the 7-hour mark.

That is not a minor issue. A 2025 meta-analysis published in GeroScience — drawing on 79 cohort studies — found that short sleep duration was associated with a 14% higher all-cause mortality risk compared to sleeping 7–8 hours. For context, the same analysis found that long sleep (9 or more hours) carried a 34% higher risk.

If you are regularly sleeping fewer than 6 hours, talk to your doctor. Short sleep can be a symptom of sleep apnea, a treatable condition that independently raises cardiovascular risk.

Why a U-curve, not a straight line

Both ends of the sleep spectrum raise your risk, which is the defining feature of the U-shaped relationship the research keeps finding. The left side of the U — short sleep — is linked to elevated cortisol, impaired glucose regulation, increased inflammation, and higher blood pressure. The right side — long sleep — is more complex.

Long sleep duration in population studies is often a marker of underlying illness, depression, or sedentary behavior rather than a cause of worse outcomes. The association is real, but the direction of causality is less clear than it is for short sleep. What most researchers agree on: aiming for 7–9 hours is where the data consistently points for adults.

Sources: GeroScience meta-analysis (2025), 79 cohort studies; CDC NCHS National Health Interview Survey Data Brief (2024); Journal of the American Heart Association (2018).

Sleep regularity may matter as much as duration

A 2023 study in the journal SLEEP (Oxford Academic) followed 88,000 adults in the UK Biobank and found that sleep regularity — going to bed and waking at consistent times — was a stronger predictor of mortality risk than sleep duration alone. Adults with the most irregular sleep patterns had a 48% higher mortality risk than the most regular sleepers.

This does not mean duration does not matter. It means both variables are in play. Consistent timing anchors your circadian rhythm, which governs hormone release, cell repair, and immune function. If you can only work on one habit, fixing your wake time every morning is the highest-leverage move — it automatically pulls your sleep timing into alignment.

What actually shortens your sleep (and what to do about it)

The most common culprits in adults 40–65 are alcohol (disrupts REM after the first half of the night), late-night screens (blue light delays melatonin release by up to 90 minutes), irregular schedules, and undiagnosed sleep apnea. Caffeine has a half-life of 5–7 hours, meaning a 3pm coffee still has half its caffeine load in your system at 8pm.

Structural interventions with the strongest evidence: a consistent wake time (including weekends), keeping your bedroom below 68°F, cutting alcohol within 3 hours of bed, and screening for sleep apnea if you snore or wake unrefreshed despite adequate hours. Cognitive Behavioral Therapy for Insomnia (CBT-I) has the most robust evidence base for chronic insomnia — stronger than sleeping pills by most clinical guidelines.

Discuss persistent sleep problems with your doctor before self-treating. Sleep apnea in particular is widely underdiagnosed and carries independent cardiovascular risk beyond what the sleep loss alone explains.

The bottom line

Seven to eight hours is where the mortality curve bottoms out. The 14% elevated risk from short sleep is not catastrophic in absolute terms, but it is consistent across studies and compounding — poor sleep also raises your risk of obesity, type 2 diabetes, hypertension, and depression, all of which feed back into longevity.

If you are reliably under 7 hours and feel fine, that feeling is misleading. Research consistently shows that chronically sleep-deprived people underestimate their own impairment. The biological cost accumulates regardless of subjective tolerance.