Two independent studies with combined data from almost 1.8 million people show the complex genetic basis of the insomnia, in which slight variants intervene in hundreds of genes. Both studies also indicate that sleep problems are related to other mental disorders, heart problems or diabetes.
Between 10% and 20% of the world population have chronic problems to start the dream, they wake up often or too early, aspects that define what is insomnia. The percentage rises up to a third more in the case of specific episodes, according to data published by the Spanish Dream Society. Although there are several environmental factors, such as stress, abuse of alcohol or other psychoactive substances, studies with twins have shown that much of the problem is in the genes. The two studies now published simultaneously in Nature Genetics show how much.
In one of the jobs, which compares the genome of 1,331,010 people (almost a third declared to be insomniac), the researchers identified more than 500 genes with some variation that intervene in the risk of suffering from this problem. "Our study shows that insomnia, like many other neuropsychiatric disorders, has to do with hundreds of genes, each with a slight effect.These genes alone do not have a special interest, what matters is their combined action on the risk of insomnia, "says a professor and geneticist at the Free University of Amsterdam and co-author of the study, Danielle Posthuma, in a note.
The genetic alterations observed in insomniacs do not appear related to the mechanisms that regulate sleep
They found that part of these genes are involved in the functionality of axons, the endings of neurons that, like capillaries, carry the nerve impulse to the adjacent nerve cells. Specifically, they observed a overexpression an excess or enrichment of the process that expresses the information encoded in the DNA in the proteins. This excess of expression was also found in neurons from specific regions of the brain, such as the frontal cortex.
What they did not find, or at least not significantly, was a relationship between these genetic variations in insomniacs and other aspects related to sleep, such as be an early riser the tendency to slumber, snoring or sudden awakenings. On the contrary, they saw a genetic correlation with other mental disorders, such as depression and anxiety, and other conditions, such as diabetes or coronary heart disease. "It is an important result because we were always looking for the causes of insomnia in the brain circuits that regulate sleep, we must change and focus on the circuits that regulate emotion, stress and tension", says the professor of neurophysiology at the Institute of Neuroscience of the Netherlands and co-author of the study, Eus Van Someren.
The another job, based on data from 450,000 Britons, confirms the genetic complexity behind insomnia. They identified at least 236 genes related to the symptoms of the disorder. As in the other study, here the authors found that the genetic basis of insomnia has little to do with the general regulation of sleep. In fact, they came back to find a overexpression gene, specifically in the genes that mediate proteolysis, or programmed degradation of the proteins of certain brain cells.
Sleep problems show a genetic correlation with physical, cardiac, diabetes or depression
Using a novel research technique called Mendelian randomization, the scientists looked for a connection between the different genetic variants and two or more health problems. Thus, as in the first study, they saw that insomniacs have up to twice the risk of suffering from coronary heart disease or symptoms typical of depression.
The senior author of this research, the genetic engineering researcher at Massachusetts General Hospital (USA), Richa Saxena, said: "Now there is a lot of hard work to find out how changes in genes lead to insomnia. In human cells, mice, fruit flies, zebrafish and other model organisms, detailed studies that define more precisely the causal links between insomnia and clinical outcomes are indispensable. " Without that, any effective treatment of insomnia without the aid of hypnotic drugs or opiates is a mere dream.