No. There is no evidence that you can train your body to need less sleep. Adults should sleep 7 or more hours a night on a regular basis (AASM and Sleep Research Society consensus), and the usual recommendation is 7 to 9 hours (NHLBI). What does happen when you cut back is that you get used to feeling tired: in lab studies, people’s sense of sleepiness levels off after the first few days while their performance keeps getting worse. A very small number of people are natural short sleepers, but that is an inherited trait, not a skill you can learn (Sleep Foundation).
How Much Sleep Do Adults Actually Need?
In 2015 the American Academy of Sleep Medicine (AASM) and the Sleep Research Society brought together a panel of 15 sleep experts to answer this question. Their joint statement is short and clear (AASM and SRS):
- Adults should sleep 7 or more hours per night on a regular basis to promote optimal health.
- Regularly sleeping less than 7 hours is associated with weight gain and obesity, diabetes, high blood pressure, heart disease and stroke, depression and a higher risk of death, as well as impaired immune function, more pain, worse performance, more errors and a greater risk of accidents.
- Sleeping more than 9 hours may be appropriate for young adults, people recovering from sleep debt and people who are ill.
The NHLBI gives the same picture: 7 to 9 hours for adults, and 8 to 10 hours for teens aged 13 to 18 (NHLBI).
Why It Feels Like You Have Adapted To Less Sleep
Many people who sleep 5 or 6 hours a night say they are used to it. The best-known test of that idea is a 2003 study by Van Dongen and colleagues at the University of Pennsylvania (Sleep, 2003). Forty-eight healthy adults aged 21 to 38 were randomly assigned to 4, 6 or 8 hours in bed per night for 14 days in a monitored lab, and compared with a group kept awake for three nights.
| What was measured | What happened with 4 or 6 hours a night |
|---|---|
| Thinking and reaction tests | Got steadily worse on every task, day after day, with bigger losses at 4 hours than at 6 |
| How sleepy people said they felt | Rose at first, then barely changed, and did not clearly separate the 6-hour and 4-hour groups |
| Overall size of the effect | Two weeks at 6 hours or less produced deficits equal to up to two nights of total sleep deprivation |
The authors concluded that even moderate sleep restriction can seriously impair waking function in healthy adults, and that participants were largely unaware of their growing deficits (Van Dongen et al.). That is the trap: the feeling adapts, the brain does not.
The NHLBI makes the same point in plain terms. After several nights of losing sleep, even just 1 to 2 hours a night, your ability to function suffers as if you had not slept at all for a day or two. Some people do not realize they are sleep deficient and still believe they function well; sleepy drivers, for example, may feel able to drive (NHLBI).
What About People Who Really Do Need Less Sleep?
They exist, but they are rare. Natural short sleepers routinely sleep about 4 to 6 hours, sleep less than 6 hours even when they have time for more, wake refreshed and stay alert all day, all without setting an alarm. Researchers believe inherited gene variants reduce their need for sleep, and the condition is not something people can train themselves to develop (Sleep Foundation).
The first gene was described in 2009: a mutation in a gene called DEC2 was linked to short sleep in a human family, and mice carrying the same mutation slept less than normal mice (He et al., Science 2009). DEC2 is also known as BHLHE41. A 2014 study found another variant of this gene in one twin who slept less, needed less recovery sleep after sleep deprivation and had fewer performance lapses while sleep deprived than the other twin (Pellegrino et al., Sleep 2014).
The key difference is how you feel. People who intentionally restrict their sleep to under 6 hours despite needing more face a higher risk of health problems such as heart attack, heart disease and type 2 diabetes (Sleep Foundation). If you need an alarm on weekdays and long weekend lie-ins to get by on 6 hours, you are not a natural short sleeper; you are short of sleep.
How To Feel Better On The Sleep You Can Get
You cannot shrink your sleep need, but you can make sure the time you do give to sleep is used well. These steps will not replace lost hours, yet they remove the extra tiredness that comes from poor timing and wasted time in bed.
Keep The Same Wake-Up Time Every Day
Get up at the same time every day, even on weekends or during vacations, and set a bedtime early enough for at least 7 to 8 hours of sleep (AASM Sleep Education). A regular schedule keeps your body clock stable, so you fall asleep faster and spend less of the night awake.
Raise Your Sleep Efficiency
Sleep efficiency is the time you are actually asleep divided by the time you spend in bed, times 100. When treating insomnia, doctors usually aim for at least 85% (Sleep Foundation). Do not go to bed until you are sleepy, and if you do not fall asleep after 20 minutes, get out of bed and do something quiet in low light (AASM). Turn off electronic devices at least 30 minutes before bed.
End The Night At The End Of A Cycle
Sleep runs in cycles that average about 90 minutes, with four to six in a typical night; the first is often 70 to 100 minutes and later ones 90 to 120 (Sleep Foundation). Waking from deep sleep can cause grogginess (Sleep Foundation), so on a night when you cannot get enough, an alarm set at the end of a cycle is kinder than one set in the middle.
If you must sleep less tonight, a sleep calculator can at least time your alarm for the end of a cycle, though fewer cycles still means less sleep.
Nap Short And Early
For adults, the best nap is usually about 20 minutes and no longer than 30, which gives a bit of light sleep without dropping into deep sleep. Experts typically recommend napping eight or more hours before bedtime, which for most people means before 3 p.m. (Sleep Foundation). The nap optimization calculator helps you pick a nap length and time that will not spoil the night.
Time Caffeine Carefully
Caffeine peaks in your blood within an hour, and you may keep feeling its effects for four to six hours; too much can cause insomnia (MedlinePlus). Use it in the morning, and avoid it in the afternoon and evening (AASM). Caffeine can mask sleepiness for a while, but it does not pay back any sleep.
Does Polyphasic Sleep Let You Sleep Less?
Polyphasic sleep means splitting sleep into more than two periods a day. Popular versions include the Uberman schedule (six 20-minute naps, about 2 hours in total), the Everyman schedule (3 hours at night plus three 20-minute naps, about 4 hours in total) and triphasic sleep (three periods totalling about 4 to 5 hours) (Sleep Foundation).
What it does: it gives you more waking hours, and some people with shift or on-call work use split sleep to fit an irregular schedule. What it does not do: research does not show that polyphasic schedules give any physical or mental advantage over sleeping in one block. None of the common schedules comes close to the recommended minimum of 7 hours, so following them means chronic sleep deprivation, slower reactions and disrupted body rhythms. People may feel more productive simply because they have more time, while their accuracy drops (Sleep Foundation).
Working shifts and need to split your sleep? The polyphasic sleep calculator lays out sleep blocks across the day. Aim for the blocks to add up to at least 7 hours in total.
The Risks Of Chronic Short Sleep
Some harms from sleep deficiency happen in an instant, such as a car crash, and others build up over time (NHLBI). Ongoing short sleep is linked to:
- Thinking and mood. Trouble learning, focusing, making decisions, controlling emotions and coping with change; sleep deficiency is also linked to depression and risk-taking (NHLBI).
- Appetite and blood sugar. Short sleep raises the hunger hormone ghrelin and lowers the fullness hormone leptin, and it leads to higher blood sugar, which may raise the risk of diabetes (NHLBI).
- Heart and blood pressure. Regularly sleeping under 7 hours is associated with high blood pressure, heart disease and stroke (AASM and SRS).
- Immunity. Ongoing sleep deficiency can make it harder to fight common infections (NHLBI).
- Safety. Sleep deficiency harms driving ability as much as or more than being drunk, and driver sleepiness is estimated to be a factor in about 100,000 crashes a year (NHLBI).
To see how many hours you are behind this week, use the sleep debt calculator. If short nights are your normal pattern, the chronic sleep deprivation risk calculator looks at your habits over the longer term.
When Should You Talk To A Doctor?
People concerned that they are sleeping too little or too much should talk to a healthcare provider (AASM and SRS). Book an appointment if, on a regular basis, you wake up groggy or unrefreshed, feel sleepy or less alert during the day, wake up often in the night, or sleep less than 6 hours on weekdays but much longer on weekends (Sleep Foundation). If you cannot sleep even when you have the time, that may be insomnia or another sleep disorder, which can be treated.
Need Less Sleep FAQs
Can Your Body Get Used To 6 Hours Of Sleep?
You may get used to how it feels, but not to the effects. In a two-week lab study, people on 6 hours a night kept getting worse on performance tests while their sleepiness ratings levelled off.
Am I A Natural Short Sleeper?
Probably not. True short sleepers are rare, sleep under 6 hours even when they have more time, and wake refreshed without an alarm and stay alert through the day.
Is 6 Hours Of Sleep Enough If It Is Good Quality?
For most adults, no. Good sleep quality matters, but experts recommend at least 7 hours, and better quality does not make up for regularly missing hours.
Can You Catch Up On Lost Sleep At The Weekend?
Extra sleep helps you recover from a short week, and sleeping more than 9 hours may be appropriate while recovering from sleep debt. It does not make a pattern of short weeknights healthy, and the AASM advises getting up at the same time every day, even on weekends.
Do Polyphasic Sleep Schedules Work?
They give you more waking hours, but research does not show any advantage over normal sleep, and the popular schedules provide far less than 7 hours, which means ongoing sleep deprivation.
Does Waking At The End Of A Sleep Cycle Mean I Need Less Sleep?
No. It can make waking up less groggy, but your total sleep need stays the same. Fewer cycles still means less sleep.