Sleep Quality Associated With Variation in Gut Microbiota Composition

A study published in Nature and Science of Sleep found that there was an association between variance in gut microbiota composition and sleep quality and cognitive performance in a group of older adults who had insomnia. These findings highlight gut microbiota as a potential indicator for auxiliary diagnosis of older adults with insomnia and cognitive decline.

Insomnia affects nearly 50% of adults 65 years and older, and it is associated with mental illness and cognitive decline. The ability of gut microbiota to modulate behavior through communication to the brain is a new concept in health, particularly in examining the effect on mental function and cognitive performance in people of older age. This study aimed to determine the relationships between microbiota and sleep and cognition in community-dwelling older adults with insomnia.

All participants were 65 years or older and responded to advertisements and community center calls for volunteers. Participants were included if they met criteria for insomnia. Insomnia symptoms were self-reported and confirmed by actigraphy recordings. All participants also participated in a short clinical interview. Participants were excluded if they had visual or hearing impairment, chronic neurological or psychiatric illness, alcohol or drug abuse, sleep apnea syndrome, restless leg syndrome, rapid eye movement sleep behavior, or periodic limb movement disorder during sleep. Participants with a Mini-Mental State Examination score below 26, indicating cognitive impairment, were also excluded.

All sleep recordings were performed with the Actiwatch activity monitor. Sleep onset and offset were determined as the first and last epoch of 10 consecutive immobile minutes. Participants also completed an Insomnia Severity Index (ISI) questionnaire. The ISI and actigraphy sleep efficiency (SE) were used as subjective and objective measurements of sleep quality.

There were 72 participants included in this study. A principal component analysis was used to test the correspondence between the cognitive measurements, with the top 2 principal components explaining 91.4% of the variance. The Multitasking Test of Median Reaction Latency (MTTLMD), which is a multitasking test that asks participants to manage conflicting information and ignore task irrelevant information, and the Spatial Working Memory Between Errors (SWMBE), which is a measure of spatial working memory that requires use of spatial memory and manipulation of visuospatial information, were selected to represent cognitive performance for further analysis.

There were 3067 bacterial amplicon sequence variants (ASV) determined and assigned to 45 phyla. Bacteroidetes and Firmicutes made up a mean (SD) of 90.5% (7.0%) of the total community, with Proteobacteria making up 5.9% (6.2%) of the community on average. The Firmicutes to Bacteroidetes ratio distribution was positively skewed.

A partial canonical correspondence analysis (pCCA) was used to examine the relationship between gut microbiota composition, insomnia, and cognitive performance, with SE and ISI representing insomnia and MTTLMD and SWMBE representing cognitive factors. The factors explained 7.6%, 7.5%, and 7.9% of the total variance in the ASV, the genus, and the family levels of taxonomy, respectively.

The study found that SE was a significant factor in all levels, MTTLMD was significant at the ASV level, and SWMBE was significant at the ASV level. The grouping of patients based on ISI categories was supported by the pCCA ordination plot for the ASV level. Several genera were found to be correlated with SE and MTTLMD after a goodness-of-fit parameter was calculated between bacterial populations and the pCCA model; for instance, Lachnoclostridium had a positive correlation with SE and a negative correlation with MTTLMD.

There were some limitations to this study. Assessment of sleep quality did not include a polysomnography recording, and gut microbiota levels and cognitive measurements could not be compared with those in a control group without insomnia. These findings cannot be generalized to younger age groups. Causality could not be inferred due to the cross-sectional nature of the study. Finally, mechanistic hypotheses based on information from amplicon sequencing and ribosomal RNA are difficult to formulate.

The researchers concluded that insomnia and cognitive decline are both associated with and explained the variance in gut microbiota composition.

Reference

Haimov I, Magzal F, Tamir S, et al. Variation in gut microbiota composition is associated with sleep quality and cognitive performance in older adults with insomnia. Nat Sci Sleep. 2022;14:1753-1767. doi:10.2147/NSS.S377114