Bodily Oddities

Short sleeper syndrome

Also called: Familial natural short sleep · FNSS

A small number of people need only 4 to 6 hours of sleep a night, wake without an alarm, and feel fine. Several gene variants that cause it have been found. Most people who sleep that little are simply sleep-deprived.

Brain Whole body Rare ability Structural
Genetic

How common

Well under 1% of people Very rare · < 0.01% About 50 families confirmed. One variant is found in about 4 per 100,000 people.

Can you do this?

These are answers from visitors, not a study.

How it works

Most adults need 7 to 9 hours of sleep1. Natural short sleepers need 4 to 6 hours. They go to bed late, get up early, and do not feel groggy or catch up at the weekend1. The pattern starts in childhood and lasts for life. It runs in families.

The first gene was found in 2009 by a team at the University of California, San Francisco. A mother and daughter who slept about 6 hours a night both carried a rare change in the gene DEC2, also called BHLHE412. Mice given the same change also slept less2. DEC2 helps run the daily body clock. The changed version appears to raise the level of orexin, a chemical that keeps the brain awake2.

Two more genes followed. A variant of ADRB1, found in 2019, occurs in about 4 in 100,000 people. A variant of NPSR1, also found in 2019, is rarer still, at fewer than 1 in 4 million3. Each gene explains only a few families, so more probably remain to be found.

How common it is

True genetic short sleepers are far fewer than 1% of the population. Only about 50 families have been confirmed3. Many more people believe they are short sleepers. Most are not. They build up sleep debt and perform worse on attention tests than they think they do4.

Short sleep with grogginess, a need for caffeine, or weekend catch-up sleep is not the syndrome. It is sleep deprivation, which raises the risk of accidents, weight gain, and illness4.

Sources and further material

  1. Encyclopedia Short sleeper syndrome
  2. Encyclopedia BHLHE41 He et al., 2009, found the DEC2 variant at the University of California, San Francisco.
  3. Encyclopedia Ying-Hui Fu Her lab found the DEC2, ADRB1 (Shi et al., 2019) and NPSR1 (Xing et al., 2019) variants.
  4. Encyclopedia Sleep deprivation
Brain Involuntary

Hypnic jerks

A sudden jolt of the arms, legs, or whole body just as you fall asleep, often with a feeling of falling. Most people get them, and they are harmless.

60–70% of people
Brain Involuntary

Exploding head syndrome

A loud bang, crash, or explosion heard inside the head while falling asleep or waking up. Nothing actually happens, there is no pain, and it is harmless.

10–37% of people, lifetime
Brain Involuntary

Sleep paralysis

You wake up, or start to fall asleep, and cannot move or speak for a few seconds to minutes. Sometimes a threatening presence seems to be in the room. It is the normal paralysis of dreaming sleep running a little late.

8–30% of people, lifetime