Abstract
Dysregulation of the gut microbiome is associated with several life-threatening conditions and thus might represent a useful target for the prevention of dementia. However, the relationship between the gut microbial population and dementia has not yet been fully clarified. We recruited outpatients visiting our memory clinic to participate in this study. Information on patient demographics, risk factors, and activities of daily living was collected, and cognitive function was assessed using neuropsychological tests and brain magnetic resonance imaging scans. Faecal samples were obtained, and the gut microbiome was assessed by terminal restriction fragment length polymorphism (T-RFLP) analysis, one of the most well-established and reliable 16S ribosomal RNA-based methods for classifying gut microbiota. Patients were divided into two groups, demented and non-demented. Multivariable logistic regression models were used to identify the variables independently associated with dementia. The T-RFLP analysis revealed differences in the composition of the gut microbiome: the number of Bacteroides (enterotype I) was lower and the number of ‘other’ bacteria (enterotype III) was higher in demented than non-demented patients. Multivariable analyses showed that the populations of enterotype I and enterotype III bacteria were strongly associated with dementia, independent of the traditional dementia biomarkers. Further studies of the metabolites of gut microbes are needed to determine the mechanism underlying this association.
Highlights
47 million people were living with dementia in 2015, and this number is projected to triple by 20501
Previous studies have revealed an association between the gut microbiome and cardiovascular disease in Japanese patients[5,6]; it remains to be established whether the composition of the gut microbiome is associated with dementia in the Japanese population
Informed consent was obtained from 181 patients who visited the memory clinic at the National Center for Geriatrics and Gerontology (NCGG) during the study period
Summary
47 million people were living with dementia in 2015, and this number is projected to triple by 20501. Recent research has identified a novel association between the gut microbiome and dementia[7,8], suggesting that the gut microbiome may modulate host brain function via a microbiome–gut– brain axis[9]. The existence of such an axis has been hypothesised because changes in the gut microbiome have been shown to be part of the mechanism linking high levels of fat consumption and other unbalanced diets with impaired cognition[9]. We aimed to investigate the relationship between the composition of the gut microbiome and dementia in Japanese patients, using a comprehensive assessment of cognitive function. We hypothesised that there would be differences in the composition of the gut microbiome between demented and non-demented patients
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