Study finds link between gut microbiota, sleep quality and cognitive flexibility

A new study highlights the link between sleep habits, gut microbiome composition and cognitive flexibility in healthy older adults, but could probiotics benefit sleep-related cognitive issues?

Led by scientists from Kent State University in Ohio, the study found that poor sleep quality was associated with lower proportions of bacteria in the phyla Verrucomicrobia and Lentisphaerae, with the former phylum also associated with performance on specific cognitive tests.

“Our findings show that lower proportions of Verrucomicrobia and Lentisphaerae are associated with poor sleep quality, raising the possibility that they contribute to metabolic dysfunction and obesity, which are commonly observed in populations with disrupted sleep,” wrote the authors in the journal Sleep Medicine.

The gut-brain axis

The gut-brain axis – that bidirectional interaction between the gastrointestinal tract and the nervous system – is gaining increasing attention from scientists and consumers. Research is linking the gut microflora to a range of health indications, from general mood to lower levels of anxiety and depression.

Evidence in the scientific literature shows that partial sleep deprivation may change the microbiota, while jet lag and shift work can also produce dysbiosis, which in turn can promote obesity and glucose intolerance.

In an extensive article in the Huffington Post, Michael Breus, PhD (a.k.a. The Sleep Doctor), discusses the sleep-gut connection, and the many ways in which the gut microbiota may influence sleep, via effects on mood, stress, pain, and hormones.

Study details

The researchers recruited 37 older adults with an average age of 65 to participate in their study. Participants provided stool samples, provided data on sleep quality using the Pittsburgh Sleep Quality Index, and completed tests of cognitive flexibility (the Stroop Color Word Test).

Results showed that better sleep was associated with both better cognitive flexibility and higher proportions of Verrucomicrobia and Lentisphaerae.

“When considered alongside previous studies, the current results suggest altered gut microbiome composition as a possible mechanism linking inadequate sleep to poor neurocognitive outcomes,” wrote the researchers. “The relationship between the gut microbiome and cognitive flexibility was insignificant after accounting for prior sleep history, suggesting that poor sleep results in both poorer cognitive flexibility and altered microbiome composition in older adults.”

“… prospective studies are necessary to determine whether altered microbiome composition mediates the relationship between sleep and cognitive decline. Such work will inform whether probiotics, which improve gut health, may buffer against sleep-related cognitive dysfunction.”

A growing consumer market
Given the consumer interest in both the gut-brain axis and the growing understanding on how sleep quality improves life, if a probiotic or prebiotic company could build a compelling scientific case then a lucrative market potentially awaits.

Commenting on the gut-brain-sleep issue earlier this year, a spokesperson for the International Probiotics Association told NutraIngredients-USA: “The potential for probiotics to influence sleep is an interesting question. The few studies that have been done have focused on stress or bowel function, and obviously if you can ease stress or anxiety or relieve digestive discomfort, then this could influence sleep.

“It may very well be that probiotics under certain circumstances can improve sleep quality, and if we dig further this could be a fruitful area of future research.”

Data from the Datamonitor Consumer 2014 survey found that “insomnia” was tied for the fourth most prominent health issue of American consumers ranked by percentage, coming in behind stress, tiredness and fatigue (which itself is related to sleep), and allergy. The most worried demographic when it comes to insomnia was middle-age women.

This has led to a rapid growth in the sleep aid category in the US, which is reported to be growing at almost 30% year-on-year and predicted to hit $732 million in 2018, according to Euromonitor International.

The category is dominated by P&G’s ZzzQuil, while natural products and dietary supplements (including melatonin and herbs like Valerian) only occupy a small portion of the market. However, market research data have repeatedly shown consumers would prefer a “natural” alternative to “synthetic” OTC products.

Source: Sleep Medicine
Volume 38, Pages 104-107, doi: 10.1016/j.sleep.2017.07.018
“A preliminary examination of gut microbiota, sleep, and cognitive flexibility in healthy older adults”
Authors: J.R. Anderson et al.