Sleep Duration and Longevity: What the U-Curve Actually Shows as You Age

The U-Curve Is Real

The idea that both too little and too much sleep are linked to shorter lives is not a myth. A 2010 meta-analysis in Sleep by Cappuccio and colleagues pooled 16 prospective studies (27 cohorts, about 1.38 million participants). Compared with the reference group, short sleepers had a 12% higher risk of death (RR 1.12) and long sleepers a 30% higher risk (RR 1.30).

A larger dose-response meta-analysis published in the Journal of the American Heart Association in 2017 (Yin and colleagues) located the bottom of the curve: the lowest risk across outcomes was seen at roughly 7 hours per day, and this varied little by sex. Below 7 hours, all-cause mortality rose by about 6% for each hour less (RR 1.06 per hour); above 7 hours, it rose by about 13% for each extra hour (RR 1.13 per hour).

Why Long Sleep Looks Riskier Than Short Sleep

The steeper slope on the long-sleep side surprises many people. But these are observational studies, and long sleep is often a marker rather than a cause. Underlying illness, depression, low physical activity, medications and undiagnosed sleep disorders can all lengthen time in bed and also raise mortality. Researchers generally caution that the data do not show that cutting sleep short would extend anyone's life.

Does the Sweet Spot Move With Age?

A popular claim says the "optimal" amount drops to about 6–6.5 hours in your 70s. Current guidelines do not support that:

• The National Sleep Foundation (Hirshkowitz et al., 2015) recommends 7–9 hours for adults aged 18–64 and 7–8 hours for adults 65 and older. It also defines "may be appropriate" ranges on either side to allow for individual variation.
• The American Academy of Sleep Medicine and Sleep Research Society (Watson et al., 2015) state that adults should sleep 7 or more hours per night on a regular basis.

What does change with age is sleep structure. A meta-analysis of 65 studies covering 3,577 healthy people aged 5 to 102 (Ohayon et al., 2004) found that in adults, total sleep time, sleep efficiency, the share of deep (slow-wave) sleep and the share of REM sleep all decline with age, while lighter sleep stages and time awake after falling asleep increase. After age 60, only sleep efficiency kept declining significantly.

So sleeping a little less, and more lightly, is common in later life. But "older adults tend to sleep less" is not the same claim as "less sleep is better for older adults." The upper end of the recommendation simply narrows from 9 to 8 hours.

Sleep Efficiency and Time in Bed

Sleep efficiency is time asleep divided by time in bed. Someone who lies down at 10 PM, falls asleep at 10:45, is awake for 20 minutes at 3 AM and gets up at 6 AM has spent 8 hours in bed but slept about 6.75 hours, an efficiency of roughly 84%.

Lying in bed far longer than you can sleep tends to go along with fragmented, frustrating nights. For chronic insomnia, the American Academy of Sleep Medicine's 2021 guideline (Edinger et al.) strongly recommends cognitive behavioral therapy for insomnia (CBT-I). Sleep restriction therapy, which deliberately limits time in bed to match actual sleep, receives a conditional recommendation. Because it can temporarily increase daytime sleepiness, it is best done with guidance from a clinician rather than improvised.

Regularity: A Strong Signal

A 2024 study in SLEEP (Windred et al.) used more than 10 million hours of wrist-accelerometer data from 60,977 UK Biobank participants to calculate a Sleep Regularity Index. Compared with the least regular fifth of participants, those with more regular sleep had a 20–48% lower risk of all-cause mortality, after adjustment for age, sex and many lifestyle and health factors. In this cohort, sleep regularity predicted mortality more strongly than sleep duration did.

Practically, this points to a simple habit: keep your wake-up time roughly the same every day, weekends included. Large weekend shifts (often called "social jet lag") work against that consistency.

Naps: Short Is Fine, Long Is a Signal

A 2015 dose-response meta-analysis in Sleep (Yamada et al.) found that daytime naps of 60 minutes or more were associated with higher all-cause mortality (RR 1.27) and cardiovascular disease (RR 1.82) compared with not napping. Naps shorter than 60 minutes were not significantly associated with either outcome, and for cardiovascular disease the risk curve was lowest around 30 minutes.

Again, this is observational: frequent long naps may reflect poor nighttime sleep or underlying illness. If you nap, keeping it short (about 30 minutes or less) and in the early afternoon is a reasonable approach.

Putting It Into Practice

• Adults under 65: aim for at least 7 hours on most nights.
• 65 and older: around 7–8 hours is the usual target, but how you function during the day is a better guide than a number on a tracker.
• At any age: a consistent wake time, enough daylight in the morning, and not staying in bed long after you have stopped sleeping.

When to Talk to a Clinician

Some sleep changes are not simply "normal aging." Consider seeing a doctor if you notice loud snoring or pauses in breathing, strong daytime sleepiness despite enough time in bed, a sudden change in your sleep over weeks, regularly needing more than 9 hours, or trouble sleeping on three or more nights a week for three months or longer.

The Bottom Line

The U-curve is real, and its lowest point sits near 7 hours. Sleep becomes lighter and less efficient with age, and recommendations for older adults narrow to 7–8 hours, but there is no good evidence that older adults should aim for 6 hours. Focus on a sufficient, regular schedule, and treat persistent problems as something worth checking rather than something to push through.