On the Potential Role of Periodontitis in the Pathogenesis of Alzheimer’s Disease

Neuroinflammation caused by activation of microglial cells plays a key role in the pathogenesis of Alzheimer's disease which can be enhanced by low grade upstream systemic inflammation and vice versa. There is growing evidence that age related chronic periodontitis drives systemic inflammation and thus finally Alzheimer's disease, therefore a causal link might exist between certain oral pathogens and Alzheimer's disease. In an own pilot study, twenty patients with probable Alzheimer's disease were investigated. In seven of these pathogenic periodontal bacteria were found. The presence of Porphyromonas gingivalis, the key pathogen and one of the species involved in chronic periodontitis, was found to be associated with lower cognitive test scores (mini mental state examination scores p <0.05; clock drawing test p = 0.056). Further, association between lower serum concentrations of immune biomarker neopterin and the presence of Treponema denticola (p <0.01). Serum neopterin concentrations correlated highly significantly with kynurenine to tryptophan ratios indicating activity of cytokine interferon-γ. These preliminary findings point to a possible role of an altered salivary microbiome as a causal link between chronic periodontitis and cognitive impairment in Alzheimer's disease.