1.3 million patient study identifies brain cells involved in insomnia.

Insomnia is a sleep disorder where people have difficulty falling asleep or staying asleep for a healthy amount of time, with over 770 million people suffering from sleeplessness worldwide.  Currently, there is no sufficient treatment available for insomnia and despite evidence pointing towards heritability, research into the associated genes and neurobiological pathways remains limited. 

Now, a study from researchers led by VU Amsterdam identifies the cell types, regions, and biological processes in the brain which mediate the genetic risk of insomnia.  The team states their study, which assesses DNA and sleeping-based features in over 1.3 million people, is a major step towards uncovering the biological mechanisms which cause insomnia. The opensource study is pre-printed in bioRxiv and published in the journal Nature Genetics.

Mapping the genetics of insomnia

Previous studies show insomnia can occur independently or as a result of another problem.  A multitude of conditions can result in insomnia such as psychological stress, chronic pain, heart failure, menopause, certain medications, and drugs like caffeine, nicotine, or alcohol.  In addition, while treatment for insomnia alleviates symptoms, most sufferers describe feeling vulnerable to experiencing poor nights of sleep.

This susceptibility to insomnia is known to run in families and appears to be hard-wired in the brain with only a few of the genes involved identified. It has also remained unclear where in the brain insomnia risk genes exert their disturbing role, knowledge which would be crucial to developing better treatments.  The current study performs genetic analysis on a 1.3 million cohort to allow the detection of genetic variants, biological functions, cell types, and tissues involved in insomnia.

The current study analyses genetic data from 1.3 million people, the largest genetic dataset ever, obtained from the UKBiobank and 23andMe databases to find out where in the brain insomnia risk genes exert their effect.  Results identified 956 genes utilized by specific biological processes, cell types, and brain areas, whose variants contributed to the risk of insomnia. 

Data findings show involvement of the axonal part of neurons, of specific cortical and subcortical tissues, and of two specific cell-types in insomnia, namely, striatal medium spiny neurons and hypothalamic neurons. These cell-types have been implicated in the regulation of reward processing, sleep, and arousal in animal studies, this is the first time they have been genetically linked to insomnia in humans.

Brain structures and insomnia

The lab explains insomnia, like so many other neuropsychiatric disorders, is influenced by hundreds of genes, each possessing a small cumulative effect.  They go on to add these genes by themselves are not of interest, however, when combined they vastly raise the risk of insomnia. 

The group concludes their findings are a breakthrough, as the global medical community can now start searching for underlying mechanisms in individual brain cells in regards to insomnia.

The team surmises their findings provide novel insight into the pathology of insomnia, implicating specific cell types, brain areas, and biological functions.  For the future, the researchers state their data is a starting point for the development of new therapeutic targets for insomnia and may also provide valuable insights for other genetically related disorders.

Source: VU Amsterdam

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