Poor Sleep Was Linked To Changes In This Beneficial Gut Bacteria

We tend to treat sleep and gut health like two separate projects. For better sleep, we dim the lights, put our phones away, and try to stick to a bedtime. For better gut health, we load up on fiber, fermented foods, and as many different plants as we can fit into a week.

But the two systems are much more connected than that.

The gut and brain are constantly communicating, and researchers have been interested in whether the trillions of microbes living in our digestive tract might be part of that conversation. Most of the research so far has focused on whether gut bacteria can influence sleep. A newer question is looking at the relationship from the other direction: Could the quality of our sleep also be reflected in the microbes living in our gut?

The study included 869 adults participating in the Baltimore Longitudinal Study of Aging, with an average age of about 71.

Researchers collected stool samples and used shotgun metagenomic sequencing, a technique that allowed them to look closely at which bacterial species were present in each person's gut. Participants also answered questions about insomnia symptoms, including how often they had trouble falling asleep, as well as how frequently they experienced excessive daytime sleepiness.

A smaller group of 332 participants wore activity monitors that objectively tracked their sleep. This gave researchers information beyond how people thought they were sleeping, including sleep efficiency and how much time they spent awake after initially falling asleep.

Researchers didn't find a simple pattern where better sleepers had a universally "healthier" or more diverse microbiome. In fact, their findings around overall microbial diversity were limited and inconsistent.

What caught my attention was how specific the association became when they looked at individual bacteria.

One species, Eubacterium sp. CAG:251, consistently showed up in connection with sleep. People who frequently experienced insomnia symptoms or excessive daytime sleepiness were more likely to have depleted or undetectable levels of this bacterium.

And when researchers looked at the wearable data, they saw a similar pattern. Better sleep efficiency was associated with a higher prevalence of Eubacterium sp. CAG:251, while spending more time awake during the night was associated with a lower prevalence. For every additional 30 minutes spent awake after initially falling asleep, the prevalence of this bacterium was lower.

This study doesn't tell us that poor sleep causes the loss of Eubacterium sp. CAG:251, or that increasing this bacterium would suddenly help someone sleep better. The researchers themselves call the findings exploratory, and because the study wasn't designed to establish cause and effect, we don't yet know which direction the relationship runs.

But it adds some nuance to how we think about both sleep and the microbiome.

We often focus on sleep duration, but spending eight hours in bed doesn't necessarily mean you're getting eight hours of restorative sleep. If you're waking frequently throughout the night, your sleep efficiency can be much lower even when your bedtime and alarm clock suggest you're getting enough rest.

And when it comes to supporting the microbiome, diet tends to get almost all the attention. Fiber diversity, fermented foods, and minimally processed foods absolutely matter, but your gut doesn't exist independently of the rest of your lifestyle. Sleep, exercise, stress, medications, and other factors can all shape its environment.