“I only sleep four or five hours a night, and I feel completely fine.”
People like this are sometimes called “short sleepers.”
You may have read about well-known executives who “only sleep a few hours a day,” and perhaps wondered, “Could I train myself to need less sleep, too?”
So, are there really people who are fully rested on less sleep than most of us?
The short answer:
True short sleepers are believed to exist.
What’s more, recent research increasingly suggests that this is not just a matter of lifestyle, and that genes may be involved.
In 2025, a study on a newly identified gene variant was also published.
Sleeping Little Doesn’t Make You a Short Sleeper
First, the most important point:
“People who sleep only a few hours” and “natural short sleepers” are two different things.
Everything else follows from this.
In particular,
if you are sleepy but pushing yourself to stay awake, you are not a short sleeper.
You get up after five hours because of work.
You need your alarm to go off again and again.
You fight off drowsiness with caffeine.
You sleep little on weekdays, then sleep in on your days off.
In cases like these, you may simply be cutting your sleep short.
Researchers study naturally short sleep with a genetic background under the name Familial Natural Short Sleep (FNSS).
People with FNSS are not deliberately cutting back on their sleep.
They wake up naturally after a short night, yet show no strong daytime sleepiness or obvious drop in functioning—that is what sets them apart.
In other words, natural short sleepers are
not “people trying hard to get by on four or five hours,” but “people who simply need less sleep to begin with.”
That is the real difference.
You can’t tell whether someone is a short sleeper just by looking at how long they sleep.
What Percentage of People Are True Short Sleepers?
So how many natural short sleepers are out there?
Online, you may come across figures such as “less than 1% of the population” or “about 1–3%.”
However, academic reviews of sleep genetics state that the exact prevalence of FNSS is unknown.
In other words, at this point,
“X% of the population are true short sleepers”
is not something science has established.
At the same time, the number of cases in which specific gene variants have been confirmed, and the number of people who have been studied, remain limited.
For that reason, natural short sleepers—people who are born able to rest fully on little sleep and function well during the day—are thought to be quite rare.
Sleeping only five hours a night doesn’t necessarily mean you are a short sleeper.
Are Short Sleepers Shaped by Their Genes?
One of the turning points in short-sleeper research was a study published in Science in 2009.
The research team studied a family of naturally short sleepers and discovered a variant in a gene called DEC2 (BHLHE41).
Research has continued since then, and variants in genes such as
ADRB1
NPSR1
GRM1
have also been linked to naturally short sleep.
In other words, rather than simply being “good at going without sleep,” natural short sleepers may have differences in the very biological mechanisms that regulate how much sleep we need and how we stay awake.
2025: A Newly Discovered SIK3 Variant
Then, in 2025, a new study was published in the Proceedings of the National Academy of Sciences (PNAS).
A research team including the Chinese Academy of Sciences and the University of California, San Francisco (UCSF) reported an N783Y variant in the SIK3 gene in a person with naturally short sleep.
SIK3 is a gene that had already been studied for its role in regulating sleep.
When the team went on to study mice carrying this variant, they confirmed that the mice slept less.
Of course, results in mice can’t be applied directly to humans.
Even so, it is an intriguing finding: a specific gene variant was found in a human natural short sleeper, and animal experiments also showed an effect on sleep duration.
Together with the other genes discovered so far, the evidence supporting the idea that
“some people are born needing less sleep”
continues to grow.
Why Are They Fine on So Little Sleep?
This raises a natural question.
“Why are they fine sleeping less than most people?”
It’s a fair thing to wonder.
Current research suggests that rather than simply being “good at going without sleep,” there may be differences in the very systems that regulate sleep homeostasis and sleep need.
So rather than simply assuming that
“they fit the eight hours of sleep most people need into four,”
a better way to put it might be:
“Their bodies and brains may simply need a different amount of sleep in the first place.”
That view is probably closer to the truth.
That said, much about the detailed mechanisms is still unknown.
Forcing Yourself to Stay Awake Is Completely Different
This point is worth stressing again.
True short sleepers are
not “people who are sleepy but stay awake through sheer willpower.”
They wake up naturally, because the sleep they need is already complete.
On the other hand, if you keep sleeping only a short time while feeling
“I still want to sleep,”
“Mornings are hard,”
“I’m sleepy during the day,” or
“I end up sleeping in on my days off,”
your body may need more sleep than it is getting.
In short:
someone who sleeps four hours and naturally wakes up refreshed, and someone who forces themselves up after four hours, are in completely different situations, even though they sleep the same amount.
That is the key difference.
Training Yourself to Be a Short Sleeper Is Another Story
The existence of true short sleepers does not mean that
“if I gradually cut back on sleep, I can become a short sleeper too.”
That is another matter entirely.
The natural short sleepers being studied did not acquire short sleep through effort; they are people who have naturally slept little all along.
In the average adult, chronic sleep deprivation is known to affect attention, judgment and mood.
What’s more, when sleep deprivation continues, people get used to it, and they may not fully notice the decline in their own performance.
“I get my work done on five hours of sleep, so I’m fine” isn’t necessarily true.
What Matters Isn’t How Much Sleep You Can Cut
Sleep needs vary from person to person.
So not everyone needs exactly the same amount of sleep.
At the same time, there is no need to make sleeping less a goal in itself.
Can you wake up naturally in the morning?
Are you free of strong daytime sleepiness?
Are you avoiding big catch-up sleep on your days off?
Are your focus and judgment holding up?
Paying attention to your own condition like this matters too.
What short-sleeper research teaches us is
not that “people can train themselves into short sleep by cutting back,” but that “the biological mechanisms that determine how much sleep we need may differ from person to person.”
Sleeping only four or five hours a night doesn’t make you a short sleeper.
If anything,
“if you are sleepy but forcing yourself to stay awake, you are not a short sleeper”
is the simpler way to look at it.
Instead of asking, “How much sleep can I cut?”
try asking:
“How much sleep do my body and brain actually need?”
Thinking about it this way leads to a healthier relationship with sleep.
At La HEAD, we will continue to share the latest research on sleep, the brain and rest in ways that are easy to bring into everyday life.