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If you’ve ever battled insomnia, you’re probably familiar with the usual suspects: stress, caffeine, alcohol, underlying health issues, or side effects from medications, to name a few.
But the key to chronic sleeplessness may lie deep in the gut – at least partly, according to a new study in the journal General Psychiatry.
About 10 per cent of adults suffer from regular insomnia, and another 20 per cent experience occasional symptoms, which include difficulty falling asleep and poor sleep quality as well as daytime effects such as irritability or fatigue.
Other research has pointed to a link between insomnia and gut health through the so-called gut-brain axis, but the latest findings offer “preliminary evidence” that the makeup of the gut microbiome can actually cause poor sleep, the study authors said.
The analysis relied on genetic data from nearly 387,000 insomnia patients as well as nearly 27,000 people’s gut microbiome data.
It identified a reciprocal link between insomnia and certain types of bacteria found in the gut. That means these bacteria raised the risk of insomnia, while having the sleep disorder also seemed to make the bacteria more common.
Fourteen groups of bacteria raised the risk of insomnia by between 1 per cent and 4 per cent. Eight groups lowered the risk by 1 per cent to 3 per cent.
People who had insomnia, meanwhile, had much lower levels of seven bacteria groups and significantly higher levels of 12 types of bacteria.
The gut microbiome consists of bacteria, fungi, and viruses that live naturally in our bodies and can both help and hurt our health. These microbes communicate with other cells to help digest food, regulate the immune system, and destroy other harmful microorganisms.
It’s not yet clear exactly why gut health and sleep appear to be connected, the researchers said. One theory is that insomnia affects the body’s level of serotonin and dopamine – chemical messengers involved in the sleep cycle – which in turn triggers the gut to produce these neurotransmitters.
Other potential pathways involve immune regulation, inflammation, and other molecular and cellular mechanisms, they said.
“Overall, the intertwined effects of insomnia on gut microbiota, and vice versa, represent a complex bidirectional relationship,” they said.
The study has some limitations. Most participants were of European descent, so the results may not apply to other groups. Diet and other lifestyle factors that could affect people’s gut health were also not taken into account.
Even so, the researchers said the findings could help inspire future microbiome-related treatments for insomnia, for example the use of probiotics, prebiotics, or faecal transplantation.