Swiss scientists say they have identified a sleep gene, which explains why some people sleep soundly through the night while others barely get a wink.
The Lausanne University team's findings, published on Friday in the scientific journal Science, could provide a basis for understanding how sleep is regulated in the different stages of human life.
As well as identifying the presence of a "normal sleep" gene, the study found that vitamin A played a role in sleep quality. However, it was unclear whether sleepless nights were caused by an excess or a lack of the vitamin.
"Our finding is important in that we show that a gene affects sleep quality - something that was unknown till now," head of the research team, Professor Mehdi Tafti, told swissinfo.
Very slow brain waves, known as delta waves, are an indication of deep, restful sleep. In many older people, insomniacs and those suffering depression there is an absence of "delta activity". These people often have broken or restless sleep.
Tests on mice
The team measured the brain activity of mice during sleep and observed that some had fewer delta waves than others. Those with less delta activity displayed abnormal behaviour patterns.
By comparing the genes of the sleep-deprived mice with the normal ones, the researchers were able to localise the gene responsible for the difference: retinoic acid receptor beta.
"The gene is necessary for the normal development of embryos in general and that of the brain in particular," Tafti said. But he added that good sleep was not just a matter of genes but was also influenced by environment.
The researchers hope their findings will ultimately bring some relief to those suffering sleepless nights.
"Future research may look at the pathway we have identified to see if there is any abnormality in insomniacs," Tafti said. "Maybe by acting there, we will be able to improve their sleep quality."
Lausanne University researchers have found a sleep gene.
The gene is called retinoic acid receptor beta.
The study also found that the vitamin A played a vital role in sleep quality.
The discovery of a sleep gene means that sleep patterns are hereditary.