If you have already fought against insomnia, you probably know the usual suspects: stress, caffeine, alcohol, underlying health problems or the side effects of drugs, to name a few.
But the key to chronic insomnia could be in the intestine, at least in part, according to a new study published in the revue General Psychiatry.
About 10 % of adults suffer from regular insomnia and 20 % have occasional symptoms, including falling asleep and poor sleep quality, as well as daytime effects such as irritability or fatigue.
Other research has highlighted a link between insomnia and intestinal health through what is called the intestine-end axis, but the last results offer “Preliminary evidence” that the composition of the intestinal microbiome can actually be the cause of poor quality sleep, the study authors said.
The analysis relied on genetic data of nearly 387,000 patients with insomnia and data from the intestinal microbiome of nearly 27,000 people.
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It highlighted a reciprocal link between insomnia and certain types of bacteria present in the intestine. This means that these bacteria increase the risk of insomnia, while suffering from this sleep disorder also seems to make these bacteria more common.
Fourteen groups of bacteria increase the risk of insomnia from 1 to 4 %. Eight groups reduce the risk of 1 to 3 %.
People with insomnia, on the other hand, had much lower levels of seven groups of bacteria and significantly higher levels of 12 types of bacteria.
The intestinal microbiome is made up of bacteria, fungi and viruses that live naturally in our body and which can both promote and harm our health. These microbes communicate with other cells to help digest food, regulate the immune system and destroy other harmful microorganisms.
According to the researchers, we do not yet know exactly why intestinal health and sleep seem to be linked. A theory is that insomnia affects the level of serotonin and dopamine in the body – chemical messengers involved in the sleep cycle – which triggers the production of these neurotransmitters by the intestine.
Other potential ways involve immune regulation, inflammation and other molecular and cellular mechanisms.
“Overall, the combined effects of insomnia on the intestinal microbiota, and vice versa, represent a complex bidirectional relationship”they said.
The study has certain limits. Most participants being of European origin, the results may not apply to other groups. The diet and other factors related to the lifestyle, likely to affect the intestinal health of people, was not taken into account either.
Despite this, the researchers said that the results could inspire future treatments for insomnia linked to the microbiome, for example the use of probiotics, prebiotics or the transplantation of fecal materials.