Suffering from sleep problems could be genetic, according to a new study.
Scientists have identified 76 new genes which are associated with sleep duration after examining nearly 500,000 Britons.
Previous studies have shown that regularly getting adequate sleep – between seven and eight hours per night – is important to health.
But insufficient sleep of six hours or fewer and excessive sleep – nine hours or more – have been linked to significant health problems.
Family studies have suggested that from 10% to 40% of variation in sleep duration may be inherited and previous genetic studies have associated variants in two gene regions with sleep duration.
For this study, scientists at the University of Exeter and the Massachusetts General Hospital examined genetic data from more than 446,000 participants in the UK Biobank who self-reported the amount of sleep they typically had.
They identified 78 gene regions – including the two previously discovered – as associated with sleep duration.
While carrying a single gene variant influenced the average amount of sleep by only a minute, participants carrying the largest number of duration-increasing variants reported an average of 22 more minutes of sleep, compared with those with the fewest.
This is comparable to other well-recognised factors that influence sleep duration.
Co-lead author Dr Samuel Jones, from the University of Exeter, said: “Finding 78 areas of the genome that influence habitual sleep duration represents a huge leap forward in our understanding of the mechanisms behind why some people need more sleep than others.
“As part of a wider body of work, our discoveries have the potential to aid the discovery of new treatments for sleep and sleep-related disorders.”
Only a few of the newly discovered gene regions overlap with an early study of insomnia and chronotype – whether someone is an early riser or a night owl.
“While we spend about a third of our life asleep, we have little knowledge of the specific genes and pathways that regulate the amount of sleep people get,” said lead author Dr Hassan Saeed Dashti.
The scientists also found that there were shared health problems for those who got too little and too much sleep.
There were shared genetic links and factors such as higher levels of body fat, symptoms of depression and fewer years of schooling, the scientists said.
In addition, people who did not get enough sleep were genetically linked to insomnia and smoking, while those who got too much sleep were linked with schizophrenia, type 2 diabetes and coronary artery disease.
The findings also support earlier conclusions that the genetics of sleep duration may be different in children than in adults.
Co-senior author Dr Richa Saxena, from Harvard Medical School, said: “While follow-up studies are required to clarify the functional impact of these variants, the associated genes are known to play a role in brain development and in the transmission of signals between neurons.
“These findings suggest themes for future investigations of the sleep-wake control centres of the brain that will help us tease apart mechanisms of disordered sleep and help understand each person’s natural set point for refreshing sleep.”
– The study is published in the journal Nature Communications.