How Gut Microbes May Affect Your Sleep
Depleting intestinal microbiota in mice throws their sleep cycles for a loop.
Posted Dec 09, 2020
The importance of gut microbiota—microorganisms including bacteria, archaea and fungi living in your digestive tract—has become increasingly clear over the last decade, and work in mice has allowed us to form even more hypotheses about how our guts and our brains are connected.
Researchers at the University of Tsukuba in Japan recently found that depleting gut microbiota in mice negatively impacted their ability to regulate cycles of sleep and wakefulness. The researchers gave mice broad-spectrum antibiotics for four weeks, obliterating the microorganisms in their guts, and then compared their intestinal contents to the intestinal content of control (non-treated) mice. When they looked at the more global effect of microbiota depletion on biological pathways, they saw that amino acid metabolism and carbohydrate metabolism were most impacted. Between the groups, they also found significant differences in 209 of the 246 metabolites detected, including metabolites related to neurotransmission (i.e. signaling between neurons), like serotonin and vitamin B6, both of which are important for sleep.
Based on that possible sleep connection, the researchers analyzed electroencephalogram (EEG) and electromyogram (EMG) data for each mouse. An EEG records brain electrical waves and an EMG evaluates nerve and muscle function, so a combination of the two techniques allowed the researchers to more holistically analyze the sleep cycles of the mice. They found that antibiotic-treated mice spent significantly less time in non-rapid eye movement sleep (NREMS) during the day, and more time in both NREMS and rapid eye movement sleep (REMS) during the night, a time when mice are usually more active. The number of REM sleep episodes was higher for antibiotic-treated mice during the day and at night, and accompanied by frequent switching from NREMS to REMS.
The researchers behind the work have hypothesized that decreased serotonin levels are behind these sleep abnormalities in antibiotic-treated mice, but the mechanism isn’t yet understood. And although it’s tempting to use this early data to draw conclusions about humans, that experiment will be far more difficult and could pose ethical challenges. Having a healthy microbiome is never a bad thing, but how much it affects your sleep is far from clear.