Genes linked to need for sleep

People who have trouble dragging themselves out of bed in the morning may now have the perfect excuse, according to research.

Scientists have found that people with a genetic variation need nearly 30 minutes more sleep a night than those without it.

The variation, found on a gene called ABCC9, is present in one in five Europeans. The scientists, from Edinburgh University and Ludwig Maximilians University, Munich, say it is the first time a gene has been found in humans that explains why some people need more sleep.

More than 10,000 people throughout Europe, including the Orkney Isles, Croatia, the Netherlands, Italy, Estonia and Germany took part in the study, and provided information on how many hours they slept each night, along with a blood sample to analyse their DNA.

Sleep was measured on "free days," when people did not need to get up for work the next day, take sleeping pills or work shifts.

People with the genetic variation needed more than eight hours sleep, the length of time the study classed as average.

Margaret Thatcher famously managed on four hours of sleep a night while Albert Einstein needed 11 – now a study suggests why. Legend also has it that Napoleon only needed four hours of sleep a night.

When the scientists blocked ABCC9 from functioning in fruit flies, which normally carry the gene, the insects slept for three hours less than normal.

The gene ABCC9 is involved in sensing energy levels of cells in the body.

The researchers also found that seasonal changes in daylight at different latitudes also appeared to have an effect on how long people sleep, but more research is needed to fully understand how time of year and geography are involved.

The scientists said the findings could open up a new line of research in sleep studies and now want to find out precisely how the gene variant regulates sleep duration.

Dr Jim Wilson, at the University of Edinburgh’s Centre for Population Health Sciences, said: "Humans sleep for approximately one-third of their lifetime.

"A tendency to sleep for longer or shorter periods often runs in families despite the fact that the amount of sleep people need can be influenced by age, latitude, season and circadian rhythms.

"These insights into the biology of sleep will be important in unravelling the health effects of sleep behaviour."

The study is published online in the journal Molecular Psychiatry.

This article was published on Mon 5 December 2011