Subgingival microbiota in a population with and without cognitive dysfunction

ABSTRACT

Aim: The aim of this study was to compare the subgingival microbiota of people with Alzheimer´s disease (AD), mild cognitive impairment (MCI), subjective cognitive decline (SCD) and cognitively healthy individuals.

Materials and methods: The study population was recruited from 2013 to 2017 and comprised 132 cases recently diagnosed with AD (n = 46), MCI (n = 40) or SCD (n = 46), and 63 cognitively healthy controls. Subgingival samples were collected, and the microbiotas were characterized by 16S rRNA gene sequencing.

Results: The relative abundance of the ten most common genera did not differ between the cases and control groups. However, the microbial richness and evenness were higher in cases than in controls and differed across the four groups. The variables with the greatest influence on the microbial community composition were related to periodontal disease followed by body mass index, study group affiliation and smoking. Ten taxa exhibited significant differences between case participants and controls. Two Operational Taxonomic Units were particularly abundant in AD compared to controls: Slackia exigua, which was also associated with deep periodontal pockets, and a Lachnospiraceae [G-7] bacterium.

Conclusion: It is concluded that in individuals with cognitive impairment or AD, the subgingival microbiota exhibits shifts typical of periodontal disease.

KEYWORDS:

• Dementia
• molecular epidemiology
• oral microbiome
• periodontal disease
• periodontal-systemic disease interactions
• RNA sequencing

Conflict of interest

None of the authors reports conflicts of interest related to this study.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

The study was supported by grants from Karolinska Institutet (Clinical Scientist Training Programme and Funds), the Patent Revenue Fund for Research in Preventive Odontology, Stockholm County Council (Steering committee KI/SLL for odontological research), the Swedish Dental Society and the Finnish Dental Association Apollonia. The study was also supported by a CIMED (Centrum för innovativ medicin) grant from Karolinska Institutet.