An international team of researchers has found, for the first time, seven risk genes for insomnia. With this finding the researchers have taken an important step towards the unravelling of the biological mechanisms that cause sleeplessness. In addition, the finding proves that insomnia is not, as is often claimed, a purely psychological condition. Today, Nature Genetics publishes the results of this research.
Insomnia is one of the most common health complaints. Even after treatment, poor sleep remains a persistent vulnerability. By having determined the risk genes for insomnia, Danielle Posthuma (VU and VUmc) and Eus Van Someren (Netherlands Institute for Neuroscience, VU and VUmc) have come a great deal closer to fulfilling a long-cherished dream: unravelling the biological mechanisms underlying this predisposition for sleeplessness.
Hope and acknowledgement for insomniacs
Professor Van Someren, specialized in sleep and sleeplessness, believes that the findings are the start of a path towards an understanding of insomnia down to the level of communication within and between neurons, and thus towards finding new ways of treatment.
It is also his hope that the findings will help with the recognition of insomnia. “In relation to the seriousness, prevalence and risks of insomnia, the research into its causes are few and far between. The problem is all too often dismissed as being ‘all in your head’. Our research brings a new perspective. It is also in the genes.”
In a sample of 113,006 individuals, the researchers found 7 genes for insomnia. These genes play a role in the regulation of transcription (the process of copying DNA in RNA) and exocytosis (the release of substances by cells in order to communicate with their environment). One of the identified genes, MEIS1, has previously been linked to two other sleep disorders: Periodic Limb Movements of Sleep (PLMS) and Restless Legs Syndrome (RLS). Strikingly, PLMS and RLS are characterized by restless movement and sensation, respectively, whereas insomnia is characterized mainly by a restless stream of consciousness.
Genetic overlap with other traits
The researchers also found a strong genetic overlap with other characteristics, such as anxiety disorders, depression and neuroticism, and with a lower feeling of general wellbeing. “This is an interesting finding, because these characteristics tend to go hand in hand with sleeplessness. We now know that this is partly due to the shared genetic basis,” says neuroscientist Anke Hammerschlag (VU), PhD-student and first author of the study.
Different genes for men and women
The researchers also studied whether the same genetic variants were important for men and women. “Part of the genetic variants turned out to be different. This suggests that, for some part, different biological mechanisms may lead to insomnia in men and women”, says professor Posthuma. “We also found a difference between men and women in terms of prevalence: in the sample we studied, and that consisted of mainly over-fifties, 33% of the women reported to suffer from insomnia. For the men this was 24%.”
The risk genes could be tracked down in cohorts with the DNA and diagnoses of many thousands of people. The UK Biobank – a large cohort from England that has DNA available – did not have information as such about the diagnosis of insomnia, but they had asked their participants whether they found it difficult to fall asleep or to have an uninterrupted sleep. By making good use of information from slaapregister.nl (the Dutch Sleep Registry), the UK Biobank was able, for the first time, to determine which of them met the insomnia profile. Linking the knowledge from these two cohorts is what made the difference.