- Insomnia shares underlying biology with major depression and abnormal glucose metabolism.
- Increased levels of excessive daytime sleepiness increases risk of schizophrenia. Genetic connections between sleep disturbance and a range of medical disorders including obesity have been identified for the first time.
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 1 in 20 people that leads to a strong urge to move one's legs, which is often worse at night. Other gene regions were important for insomnia, but selectively in either men or women.
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 team identified genetic links between longer sleep duration and schizophrenia risk and between increased levels of excessive daytime sleepiness and measures of obesity (body mass index and waist circumference). The research also suggested that insomnia has shared underlying biology with major depression and abnormal glucose metabolism.
Rutter says, "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."
UK Biobank aims to improving the prevention, diagnosis and treatment of a wide range of serious and life-threatening illnesses. Lane says, "We're particularly pleased to be able to use UK Biobank data in this way; it's an amazing resource for scientists."
Saxena adds, "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"
The authors suggest that these findings will need further study, but this knowledge amounts to a key advance in the understanding of the biology behind sleep - a major influence on our health and behaviour.
- Jacqueline Lane et al., Genetics link sleep disturbance with restless legs syndrome, schizophrenia and obesity, Nature Genetics (2016), http://dx.doi.org/10.1038/ng.3749.
- Jie Zhang, Continual-Activation Theories of Schizophrenia and Restless Legs Syndrome, http://www.goertzel.org/dynapsyc/2005/ZhangSZ.htm.