By TAP Integrative

Poor sleep often precedes cognitive decline, but the reason for this association is not well understood. Sleep restriction has been shown in humans to alter the composition of the gut microbiome, and changes in the gut microbiome have been shown in animal models to reduce cognitive flexibility. Researchers, therefore, hypothesized that changes in the gut microbiome might mediate the relationship between poor sleep and the cognitive decline of aging. 

In a cross-sectional study, 37 adults between the ages of 50 and 85 (mean age = 65 years) provided stool samples, completed questionnaires, and underwent cognitive testing. The Pittsburgh Sleep Quality Index assessed self-reported sleep quality, the Stroop Color-Word Test assessed cognitive flexibility, and the Ubiome Company completed 16S rRNA sequencing of stool samples, following protocols from the Human Microbiome Project.  

 After controlling for hypertension and carbohydrate intake, results showed that poor sleep quality was associated with poorer performance on the Stroop Word and Color-Word tests and with lower proportions of the phyla Verrucomicrobia and Lentisphaerae. The proportion of Verrucomicrobia showed a positive correlation with Stroop Word performance, but this association was not independent of sleep. Partial correlations showed that the only independent association was between poor sleep quality and poorer Stroop Color-Word performance. 

The results of this observational study do not support the hypothesis that changes in the microbiome mediate the relationship between sleep and cognition. Instead, the results suggest that poor sleep contributes to both an altered microbiome composition and poorer cognitive flexibility and in older adults.  

The small sample size and the cross-sectional design are important study limitations. It is possible that future studies will better inform clinicians whether probiotics or other interventions to improve the health of the gut might buffer against sleep-related cognitive decline.  At this time, however, it appears that improvement in sleep could improve both diversity of the microbiome as well as cognitive performance. 

Reference  

Anderson, J. R. et al. A preliminary examination of gut microbiota, sleep, and cognitive flexibility in healthy older adults. Sleep Med 38, 104-107 (2017). 


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