Genetics helps explain why some people need only a few hours of sleep
Rare mutations and hundreds of common variants appear to influence how long we sleep, according to research compiled by the BBC; sleeping little, however, does not always come free.
Translated from the Portuguese original by the Panorama newsroom. Read in Portuguese
Summary written by the Panorama newsroom from the sources listed below. Facts are attributed to the original publications.
In recent years scientists have identified several ways in which genetics influences how much sleep each person needs, from rare mutations to hundreds of common variants in the genome, BBC News Mundo reported in a story originally published by BBC Future.
One example is Aimee Pugh Bernard, an immunology professor at the University of Colorado, who usually wakes up near 4:30 a.m. full of energy. In 2019 she found the possible explanation: she carries a mutation identified by a team at the University of California, San Francisco, linked to an inherited condition called familial natural short sleep (FNSS), whose carriers usually sleep four to six and a half hours a night.
According to the team's leader, molecular biologist Ying-Hui Fu, these people seem to be fine despite getting little sleep. In a 2019 experiment, mice with an FNSS-linked mutation slept less and appeared protected against memory deficits. In 2014, a study of fraternal twins showed that the twin carrying one of these mutations slept about an hour less and, after 38 hours awake, made about 40% fewer errors on performance tests.
For most people, however, the effect is diffuse. A not-yet-published analysis of data from nearly 650,000 adults identified about 244 regions of the genome linked to sleep duration, each with an effect of about one minute, according to geneticist Isabelle Austin-Zimmerman of King's College London. Other work by her team indicated that, in general, variants associated with sleeping less were also linked to a higher risk of insomnia, tiredness, ADHD, depressive symptoms and type 2 diabetes, which does not necessarily mean that short sleep causes these problems.
The report also notes that people do not always notice the effects of sleep loss: in one study, adults limited to four to six hours in bed performed increasingly worse on cognitive tests but, after two weeks, said they felt only slightly sleepy. To become a drug, Fu says, the discovery first requires understanding how these mechanisms work, or risks unexpected side effects.