Universal injustice: why some people only need a few hours of sleep each day.

For most people on the planet, getting less than seven hours of sleep results in drowsiness, sluggish thinking, and an overwhelming desire to crawl back into bed. However, some individuals can wake up feeling refreshed and energized even after six hours of sleep or less. What a universal injustice this seems to be! Scientists have provided an answer to this question, as reported by Popular Science.

It is well-known that sleep is essential for the human body to recover and rejuvenate, but why do some people manage to restore themselves in just a few hours? Researchers have been trying to decode the mystery of "naturally short sleepers" for years, but their rarity means there are only a few studies on this phenomenon.

As early as 2009, neurology professor In-Hui Fu and a team from the University of California, San Francisco, discovered a mutation in the differentiated embryonic chondrocyte 2 gene (DEC2) in two naturally short sleepers—a mother and her adult daughter. Subsequently, the scientists bred mice with the same mutation and found that these animals slept less than their typical counterparts.

In 2018, another study revealed that the DEC2 gene mutation affects the level of orexin, a hormone that regulates wakefulness. Normally, this gene inhibits orexin production in the evening and ramps it up again before dawn. However, in individuals who are naturally short sleepers, the effect of the DEC2 gene is weaker, leading to increased orexin production and longer waking hours.

A decade after the initial research, Professor Fu's lab discovered something equally intriguing: a mutation in the beta-1 adrenergic receptor gene (ADRB1). The researchers sought to understand the effects of this mutation: the team created mice with the same mutation, and these animals also slept less.

Further investigation showed that the ADRB1 gene is highly active in the dorsal pons, a part of the brainstem that helps regulate sleep. The researchers then stimulated the neurons triggering the gene in this area and found that the mice instantly woke up. Equally interesting was the observation that the mice with the mutation had a higher proportion of wake-promoting neurons that activated more easily. The team's results also indicated that the ADRB1 gene mutation reconfigures the brain for wakefulness, shortening sleep and facilitating awakening.

Three weeks after the second study, Professor Fu and colleagues identified a third "short sleep gene." This unusual gene was found in a father and son who slept only 5.5 and 4.3 hours per day, respectively. The researchers discovered that this mutation affects the neuropeptide S receptor 1 gene (NPSR1), which helps regulate wakefulness.

The authors of the study created mice with the same mutation and found that these animals slept less and moved more. Interestingly, sleep-deprived mice with the NPSR1 mutation performed better in memory tests compared to sleep-deprived mice without the mutation. This suggests that the mutation allows naturally short sleepers to maintain cognitive function and avoid memory problems.

In 2021, Professor Fu's team continued their research and discovered a fourth gene associated with natural short sleep. The team identified two different mutations in the metabotropic glutamate receptor 1 gene (mGluR1) in two unrelated families of short sleepers. The results indicate that mice with either of these mutations slept less. Moreover, further research showed that the gene mutations likely increased the activity of nerve cells in the brains of the animals.

Can You Learn to Sleep Less?

According to Dr. Elizabeth Klerman, a neurology professor at Massachusetts General Hospital and Harvard Medical School, genetics is not the only factor affecting the amount of sleep a person needs. Age is another factor; for example, infants, young children, and teenagers require more sleep than adults to support their growth and development.

Still, Professor Klerman believes that people cannot learn to sleep less. The amount of sleep required is determined by biology, particularly age and genetics. At the same time, there is no evidence that lifestyle can somehow influence sleep needs.

Most of us need about seven to nine hours of sleep per night. Anything less can lead to sluggish thinking and slower reactions, as well as increase the risk of long-term health issues.

This material is for informational purposes only and does not contain advice that may affect your health. If you are experiencing problems, consult a specialist.