Variations in a gene that affects levels of a key brain chemical could influence how soundly people sleep, Swiss researchers say. The scientists, based at the University of Zurich, found that people with a particular version of the adenosine deaminase gene sleep more deeply. The team, who published their findings in the Proceedings of the National Academies of Sciences, also found that variations in another, related gene affected brain activity, and also how they react to caffeine.
Previous research on animals had suggested that sleep is influenced by genes, but the underlying biological basis for these findings was unclear, according to study author Hans-Peter Landolt. His team decided to look at the adenosine 'brain communication' system, since adenosine is thought to act induce sleep by acting on specific receptors. Chemicals that block these receptors - such as caffeine - increase alertness.
The scientists studied 32 people, and found that those who had a version of the adenosine deaminase gene responsible for higher brain levels of adenosine slept more deeply than those who did not have it. They also found that people with a particular version of the gene that makes the adenosine A2A receptor protein had altered brain activity, both during sleep and while awake. People with this variation also responded differently to caffeine. Together, the findings show that adenosine plays a direct role in people's sleep quality, says Landolt.
The research suggests that the adenosine system may be an important target for drugs aimed at treating sleep disturbances, say the team. Flavia Consens, of the Sleep Disorders Center at the University of Michigan, said that the study provides the first example of a gene involved in individual variability in human sleep. She added that now this has been shown, 'potentially there is always a role for a drug or intervention'.