Why some people need more sleep is in our genes, a new study suggests.
A new study by University researchers finds that one in five Europeans carry a variation of a gene known as ABCC9, which is involved in sensing energy levels of cells in the body.
People with the gene need almost 30 minutes more sleep each night than those who do not have it.
Experts say the finding opens up a new line of research in sleep studies and it is hoped that future studies will establish precisely how the gene variant regulates sleep duration.
Scientists at the University of Edinburgh - working with colleagues at Ludwig Maximilians University in Munich - made the discovery by studying human sleep patterns and genes in flies.
They found that flies without ABCC9 slept for three hours less than normal.
In humans, presence of the gene variant explained the need for some people to sleep longer than eight hours - the length of time the study classed as average.
More than 10,000 people throughout Europe took part in the study providing information on how many hours they sleep 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.
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.