Every night’s sleep is different, and how you sleep on any given night is likely to be determined largely by short-term causes – what and when you ate, how much exercise you did today, stress levels, what you watched on TV, whether your partner is snoring – but there are also fundamental, long-term differences between people in their sleep patterns. It is thought these differences are often genetic, and recent research supports this idea, identifying for the first time a gene involved in determining how much sleep we need.

Sleep is a huge part of our lives, and the lives of many animals. Although we still do not fully understand the strange phenomenon that takes up a third of our lives, it is clear that without it we cannot survive. But with a growing number of things keeping us awake – work, tv, friends, sport, buzzfeed, reddit – how much sleep is enough sleep?

Research has previously shown large differences between people in the amount of sleep they need, and these differences appear to be determined genetically. Mutations in the hPer2 gene are associated with Familial advanced sleep phase syndrome, which causes them to wake on average 4 hours earlier in the morning. This gene is thought to be analogous to the period gene in fruit flies, which is known to regulate the internal daily clock. More recently, mutations in the aptly-named clock gene have been linked to differences in sleep duration. People also differ in their sleeping patterns (only a small percentage of the population are true early birds), and these differences are largely genetic in origin.

A new study published in Sleep earlier this year found a genetic variant that allows the bearer to live comfortably and function normally on less than 6 hours sleep. By comparing sleep patterns in 100 pairs of twins, researchers showed that a variant of the BHLHE41 gene, known as p.Tyr362His (catchy, huh?) was associated with individuals who slept on average just five hours a night. Twins not carrying this variant of the gene slept on average an hour and five minutes longer each night.

The mutation also provides resistance to the effects of sleep deprivation; twins carrying the mutation made mistakes 40% less often during 38 hours of sleep deprivation, and took less time to recover afterwards. Twins without the variant needed an hour and a half longer to sleep off the effects of deprivation.

According to Dr Timothy Morgenthaler from the American Academy of Sleep Medicine (AASM), “This study emphasizes that our need for sleep is a biological requirement, not a personal preference”, adding that “most adults appear to need at least seven hours of quality sleep each night for optimal health, productivity and daytime alertness.” The AASM claims that the majority of people who regularly sleep for less than 7 hours a night are denying themselves needed sleep and are characterised as suffering from insufficient sleep syndrome. Doing so may be impairing their ability to remain alert and awake. This syndrome is currently estimated to affect 28% of US adults and has been linked to increased sleepiness, decreased energy levels and concentration and and increased risk of depression, road and workplace accidents.

Want to Know More?

• Pellegrino et al 2014 A novel BHLHE41 variant is associated with short sleep and resistance to sleep deprivation in humans
• Allebrandta et al 2010 CLOCK Gene Variants Associate with Sleep Duration in Two Independent Populations
• Toh et al 2001 An hPer2 Phosphorylation Site Mutation in Familial Advanced Sleep Phase Syndrome