A team of American and British scientists have discovered genetic connections between sleep disturbance and a range of medical disorders including obesity (The University of Manchester, 2016).

Lead author Dr Jacqueline Lane, postdoctoral fellow at Massachusetts General Hospital (MGH) and joint senior authors Richa Saxena, Assistant Professor of Anaesthesia at the MGH and Harvard Medical School and Dr Martin K Rutter, Senior Lecturer in Cardiometabolic Medicine from the University of Manchester, have published their research in Nature Genetics.

The study looked at the biological controllers of sleep duration, insomnia and excessive daytime sleepiness, and how they linked to the health and life histories of more than 112,000 people taking part in the UK Biobank study. Study participants reported their sleep duration, the degree of insomnia and daytime sleepiness, and then had their genes mapped. Other information about them such as their weight and any diseases they suffered from was also collected.

The researchers identified for the first time areas of the genome that are associated with sleep disturbance including insomnia and excessive daytime sleepiness and also discovered novel genetic links with several medical conditions including restless legs syndrome, schizophrenia and obesity.

The strongest genetic association for insomnia symptoms fell within a gene previously linked to restless legs syndrome, a nervous system disorder affecting around one in twenty people that leads to a strong urge to move the legs which is often worse at night. Other gene regions were important for insomnia but selectively in either men or women.

The team also identified genetic links between longer sleep duration and schizophrenia risk and between increased levels of excessive daytime sleepiness and higher BMI and waist circumference.

The research also suggested that insomnia has shared underlying biology with major depression and abnormal glucose metabolism.

Martin Rutter said “Scientists have long observed a connection between sleep disorders and these conditions in epidemiological studies. But this is the first time these biological links have been identified at a molecular level.”

The study was funded by the US National Institutes of Health and The University of Manchester’s Research Innovation Fund, and marks a major advance in the understanding of the biology of sleep.

One in four British adults are obese, according to the UN Food and Agriculture Organisation, prompting fears that the UK has become the “fat man of Europe”. And at any one time about 280,000 people are being treated for schizophrenia by the NHS. Sufferers have a one in ten chance of dying by their own hand within ten years of diagnosis.

Martin Rutter said “This clinical science is an important step forwards in understanding the biological basis for these conditions so it’s very exciting. Scientists have long observed a connection between sleep disorders and these conditions in epidemiological studies. But this is the first time these biological links have been identified at a molecular level.”

Jacqueline Lane said ”We’re particularly pleased to be able to use UK Biobank data in this way; it’s an amazing resource for scientists.”

Richa Saxena said “It’s important to remember there is no molecular targeting available for conditions which affect sleep: all we really have are sedatives. So we hope that this research will enable scientists to develop new ways to intervene on a range of conditions in a much more fundamental way. We do acknowledge these findings will need further study, but believe this knowledge amounts to a key advance in our understanding of the biology behind sleep – a major influence on our health and behaviour.”