A few people truly thrive on six hours of sleep, but most of us don’t

Key takeaways

• After weighing 5,314 scientific articles, two leading sleep medicine groups agreed in 2015 that adults need at least 7 hours of sleep a night, as a regular habit¹.
• Genetic “natural short sleepers” exist, but they are rare: by 2019, researchers had identified more than 50 families with members who need less than 6.5 hours a night².
• In a Japanese lab study, young men who felt fine on about 7.4 hours a night settled at about 8.4 hours when given 12 hours in bed, revealing roughly an hour of nightly debt they hadn’t noticed³.
• Big studies link long sleep to earlier death, but the researchers suggest long sleep may be a marker of illness, depression or other problems rather than a cause⁴⁵.
• A two-week home experiment, one week to repay debt and one to measure, can estimate your own need.

In 2009, a team at the University of California, San Francisco, described two women who seemed to bend a rule of human biology⁶. A mother and her daughter routinely slept about 6.25 hours a night, and both seemed healthy and well rested⁷. Relatives who didn’t share the trait slept about 8⁷.

Both women carried the same rare change in a gene called DEC2⁶. When the scientists checked 250 people outside the family, none had it⁷.

The finding put a gene behind something many people say about themselves: “I just don’t need much sleep.” A few of them are right. Most probably are not.

Your need is personal, and genes, age and health all move it. But feeling fine on less sleep doesn’t prove you need less. This guide covers what the research shows, and a two-week test to find your own number.

The expert floor is 7 hours, but the panels drew it a little differently

In 2015, 15 experts convened by the American Academy of Sleep Medicine (AASM) and the Sleep Research Society (SRS) spent a year sorting through 5,314 articles on sleep and health¹.

Their answer: for good health, adults need at least 7 hours a night, night after night¹. Regularly sleeping less was linked to weight gain, diabetes, high blood pressure, heart disease, stroke, depression, weaker immunity, accidents and a higher risk of death¹.

The panel added caveats. More than 9 hours may suit young adults, people recovering from sleep debt and people who are ill¹. Needs vary with genes, habits, health and surroundings¹. And the statement covered only adults 18 to 60¹.

That same year, the National Sleep Foundation (NSF) published its own ranges. Its 18-member panel included representatives of 12 professional groups, among them the American Academy of Pediatrics and the American Geriatrics Society⁸.

The NSF is an advocacy nonprofit that has received drug-company funding, according to 2005 reporting. The Sacramento Bee found that more than half of its $2.6 million in 2003 revenue came from drug companies, including Sanofi-Aventis, then the marketer of the sleeping pill Ambien⁹. Its funding today may look different.

The NSF marked a “may be appropriate” zone on each side of its main range, an open nod to individual differences⁸. The National Heart, Lung, and Blood Institute (NHLBI), part of NIH, uses a simpler 7 to 8 hours for everyone 18 and older, while noting that people’s needs differ¹⁰.

Age	NSF recommended	NSF “may be appropriate”	AASM and SRS	NHLBI
18 to 25	7 to 9 hours	6, or 10 to 11	7 or more; over 9 may suit young adults	7 to 8
26 to 64	7 to 9 hours	6, or 10	7 or more (statement covers ages 18 to 60)	7 to 8
65 and older	7 to 8 hours	5 to 6, or 9	Not covered	7 to 8

The three groups differ at the edges, but all put 7 hours at the bottom of the main range for adults¹⁸¹⁰. The NSF panel added that straying far outside its ranges is rare and can signal a health problem or deliberate sleep cutting⁸.

True short sleepers are born, not made

The DEC2 family was the first. In 2019, the UCSF lab of Ying-Hui Fu and Louis Ptáček traced short sleep across three generations of one family to a rare change in a gene called ADRB1². Mice engineered to carry it slept nearly an hour less each day than ordinary mice². By then, other studies had turned up more than 50 families with members who need less than 6.5 hours a night².

In May 2025, a team led from the Chinese Academy of Sciences, with Fu and Ptáček among the coauthors, reported a short-sleep mutation in a gene called SIK3¹¹. We couldn’t open the journal paper. According to the science news site ScienceAlert, the carrier was a healthy woman in her 70s who averaged 6.3 hours a night, and hers was the fifth such mutation identified¹¹. Mice with the change slept only about half an hour less than usual¹¹.

A few patterns run through this work:

• The trait runs in families and lasts a lifetime. The mother and daughter in the first study had always needed less sleep⁶.
• Each gene explains only a sliver. When the DEC2 finding came out, sleep researcher Mehdi Tafti of Switzerland’s University of Lausanne estimated that it accounted for less than 1% of short sleepers⁷.
• No single switch controls sleep. Ptáček has said that no one gene or brain region tells the body when to sleep or wake².
• The sleep itself may be better. Fu has said natural short sleepers have higher sleep quality and efficiency².

We found no reliable count of natural short sleepers. The confirmed ones were found through family studies and gene sequencing, not by asking people how they feel²⁶.

Many self-described short sleepers are running a debt they can’t feel

In a 2016 study at Japan’s National Center of Neurology and Psychiatry, researchers gave 15 healthy young men the chance to sleep as much as their bodies wanted³. After two lab nights with a standard 8 hours in bed, the men spent nine nights in a row with 12 hours in bed³.

At home, the men averaged about 7.4 hours a night, and none reported problems such as sleepiness³. In the lab, the first night of extra time produced a rebound of more than three hours³. Their sleep then tapered and leveled off after about four nights, at an average of about 8.4 hours³.

The authors called that gap, about an hour a night, potential sleep debt³. Thirteen of the 15 men had been sleeping less at home than their bodies settled on in the lab³. Their estimated needs ranged from about 7.3 to 9.3 hours, a two-hour spread among similar young men³.

After the nine nights, their blood sugar had dipped and the stress hormone cortisol had fallen³. The study was small, all male and done in a lab, so its numbers won’t fit everyone. But its lesson matches Tafti’s 2009 warning that ordinary sleepers cut back to about six hours show effects within a few days⁷.

Feeling fine is a poor gauge. A better clue, according to the NHLBI, is sleeping more on days off than on workdays¹⁰.

Long sleep tracks with earlier death, but that doesn’t mean sleep is the threat

In 2010, researchers led by Francesco Cappuccio of the University of Warwick in England pooled 16 studies that followed more than 1.38 million people for 4 to 25 years⁴. About 112,600 of them died during follow-up⁴.

Short sleepers had a 12% higher risk of dying during the studies than people who slept a middle amount⁴. Long sleepers had a 30% higher risk⁴. A 2011 analysis by the same group linked long sleep to a 65% higher risk of stroke⁵.

Most of the studies compared people with those sleeping 7 to 8 hours; long sleep usually meant more than 8 or 9 hours⁵.

The authors urged caution. They wrote that long sleep may be a marker of disease rather than a cause, and that no study had shown how it could lead to heart disease⁵.

Two problems separate a link from a cause:

• Confounding is when a third factor drives both things. Depression, low income, unemployment, little physical activity and undiagnosed illness are all tied to long sleep and to poor health⁵. Sleep apnea, a breathing disorder that breaks up sleep, wasn’t ruled out either⁵.
• Reverse causation is when the outcome comes first. Someone in the early stage of an illness may sleep more because of it. The authors tried to limit this by dropping studies with less than three years of follow-up, but they couldn’t remove it entirely⁵.

Every study also relied on people’s own estimates of their sleep⁵.

The practical point: if you need 9 hours to feel good and you do feel good, these studies give you no reason to cut back. If you sleep long and still wake tired, get a checkup. The NHLBI says that sleeping more than 8 hours without feeling rested may point to a sleep disorder or another health problem¹⁰.

Your need changes with age, and experts split on older adults

For children’s ranges by age, see our article on busy parents.

Young adults sit at the high end. The AASM panel named them as a group for whom more than 9 hours may be right, and the NSF’s “may be appropriate” range for ages 18 to 25 stretches to 11 hours¹⁸.

Older adults are the hardest case. In a 2008 study, Elizabeth Klerman of Brigham and Women’s Hospital in Boston and Derk-Jan Dijk of England’s University of Surrey had healthy volunteers spend 16 hours a day in bed, in the dark, for several days¹². Adults 18 to 32 slept about 9 hours. Adults 60 to 72 slept about 7.5 and took longer to drift off¹².

To Klerman, the most economical explanation was a smaller sleep need in later life¹². She allowed another: older people may sleep less even when they are given time for more¹². The NSF’s main range for people 65 and older is slightly lower, at 7 to 8 hours, while the NHLBI’s chart has no separate line for older adults⁸¹⁰.

Klerman also drew a warning from her results. Older adults who believe they need more sleep than they can get may decide they have insomnia and start taking medicines they don’t need¹². But an older adult who is tired during the day should be checked for a sleep disorder¹².

A two-week experiment to find your sleep need

Natural-health traditions hold that bodies differ and that the body’s own signals deserve respect. Sleep research agrees on the first point and adds a caution on the second. Your body’s signals are honest when you give them room, and misleading when you’re carrying debt.

You can borrow a sleep lab’s logic at home. In the Japanese study, extra time in bed first repaid old debt, then sleep leveled off at each man’s own need within about four days³. This test uses one week to repay and one to measure.

Pick two weeks when you can skip the alarm, such as a vacation at home. Avoid travel, illness and big deadlines, and keep caffeine, alcohol and exercise habits as usual. Fill in a sleep diary each morning; the NHLBI offers a free printable one¹⁴.

Days	What to do	What to write down
Days 1 to 7: repay	Go to bed at a set time when you feel sleepy. Wake without an alarm. Allow up to 10 hours in bed	Bedtime, wake time, rough hours asleep, plus your usual workday hours for comparison. Expect long nights at first
Days 8 to 14: measure	Keep the same bedtime. Still no alarm	Hours asleep each night, and how alert you feel at midafternoon, from 0 to 10
Day 15: do the math	Average your hours asleep for days 8 to 14	A rough estimate of your need
After the test	Count back from your usual alarm by your estimate, plus the time it usually takes you to fall asleep	Your target bedtime

How to read your results:

• Week two looks like your usual nights. You were probably getting enough already.
• Week two runs an hour or more longer than your workday nights. You’ve likely been short. Most volunteers in the Japanese study carried about an hour of hidden debt³.
• You sleep long and still wake unrefreshed, or can’t sleep despite every chance. Talk with a clinician¹⁰¹⁴.

This experiment is our adaptation of lab methods, not a validated test. Results will be off during illness, shift work, heavy stress or nights with a new baby.

What the evidence shows

Claim	Evidence level	What it rests on
Most adults need 7 or more hours a night for good health	Strong evidence	Expert review of 5,314 articles across nine health areas1
Some people are born needing about 6 hours or less	Promising but early	Real, but confirmed through a few gene changes in a limited number of families, plus mouse studies2611
You can train yourself to need less sleep	Not enough evidence	We found no study showing it; lab volunteers didn’t notice their own debt37
Sleeping 9 hours or more shortens your life	Not enough evidence	Large studies show a link, but the authors call long sleep a likely marker of illness, not a proven cause45
A week or more of extra time in bed reveals hidden debt	Promising but early	Small lab studies of healthy volunteers312
Older adults need less sleep than younger adults	Promising but early	One lab study and expert ranges point that way; whether it’s need or ability is debated812

When to see a clinician

Sometimes tiredness isn’t about need or debt at all. See a clinician if you notice:

• loud snoring, snorting, gasping or choking sounds, or short pauses in your breathing¹³;
• frequent sleepiness during the day, or falling asleep at the wrong times¹³;
• trouble falling or staying asleep 3 or more nights a week for 3 months or longer¹⁴;
• creeping or tingling feelings in your legs that ease when you move or rub them¹³;
• kicking, punching or shouting in your sleep as if acting out a dream¹⁵;
• nights of more than 8 hours that still leave you unrefreshed¹⁰.

If you nod off while driving, pull over somewhere safe, then get checked: falling asleep at the wrong times is a warning sign¹³. If poor sleep comes with hopelessness or thoughts of harming yourself, call or text 988. Our upcoming articles on sleep disorders (topics 235 to 241) go deeper.

Questions readers ask

The bottom line

Most adults do best with 7 or more hours of sleep, and some need 9 or more. A rare few are born needing about 6, but they’ve been found through family genetics, not self-reporting. If you think you’re one of them, test it.

Long sleep isn’t a worry when you wake refreshed, and long nights that still leave you tired are a reason to see a clinician. A practical way to learn your own need is to give your body extra time in bed for two weeks and see where it settles.

Related reading

• Wellness advice is written for an average person who doesn’t exist
• Most of us misjudge our own habits, and a one-week audit shows the gaps
• Busy parents need a few anchors more than a perfect routine
• Sleep trackers count your hours well, but their sleep stages are rough guesses
• Your sleep schedule may matter as much as your hours, so start with your wake-up time

Sources

1. Watson NF, Badr MS, Belenky G, et al. “Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society.” Journal of Clinical Sleep Medicine, 2015;11(6):591-592. aasm.org
2. National Institutes of Health. “Gene identified in people who need little sleep.” NIH Research Matters, September 17, 2019 (on Shi G, et al., Neuron, 2019). nih.gov
3. Kitamura S, Katayose Y, Nakazaki K, et al. “Estimating individual optimal sleep duration and potential sleep debt.” Scientific Reports, 2016;6:35812. link.springer.com
4. Cappuccio FP, D’Elia L, Strazzullo P, Miller MA. “Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies.” Sleep, 2010;33(5):585-592 (abstract, University of Warwick). text.www2.warwick.ac.uk
5. Cappuccio FP, Cooper D, D’Elia L, Strazzullo P, Miller MA. “Sleep duration predicts cardiovascular outcomes: a systematic review and meta-analysis of prospective studies.” European Heart Journal, 2011;32:1484-1492. text.www2.warwick.ac.uk
6. University of California, San Francisco. “First human gene implicated in regulating length of human sleep.” UCSF News, August 13, 2009 (on He Y, et al., Science, 2009). ucsf.edu
7. Scientific American. “Rare Genetic Mutation Lets Some People Function with Less Sleep.” 2009. scientificamerican.com
8. Hirshkowitz M, Whiton K, Albert SM, et al. “National Sleep Foundation’s sleep time duration recommendations: methodology and results summary.” Sleep Health, 2015;1:40-43. nursesinaidscare.org
9. Griffith D, Wiegand S. “Health groups’ funding faulted.” Sacramento Bee, June 26, 2005 (reproduced by Healthy Skepticism). healthyskepticism.org
10. National Heart, Lung, and Blood Institute. “Sleep Deprivation and Deficiency: How Much Sleep Is Enough?” NIH, updated March 24, 2022. nhlbi.nih.gov
11. Nield D. ScienceAlert report, May 8, 2025, on Chen H, Xing Y, Wan C, et al. “The SIK3-N783Y mutation is associated with the human natural short sleep trait.” Proceedings of the National Academy of Sciences, 2025;122(19). sciencealert.com
12. Cell Press. “Older People May Need Less Sleep, Study Finds” (on Klerman EB, Dijk DJ, Current Biology, 2008). ScienceDaily, July 25, 2008. sciencedaily.com
13. MedlinePlus. “Sleep Disorders.” National Library of Medicine, updated December 4, 2025. medlineplus.gov
14. National Heart, Lung, and Blood Institute. “Insomnia: Diagnosis.” NIH, updated March 24, 2022. nhlbi.nih.gov
15. American Academy of Sleep Medicine. “REM Sleep Behavior Disorder.” Sleep Education, 2021 (reviewed by Andrea Matsumura, MD). sleepeducation.org