Periodontal disease is associated with cognitive dysfunction in aging dogs: A blinded prospective comparison of visual periodontal and cognitive questionnaire scores

BACKGROUND: Periodontal disease has been linked to the development of Alzheimer’s disease in people. It is theorized that the chronic inflammatory condition characteristic of oral dysbiosis in patients with periodontal disease leads to disruption of the blood–brain barrier, cytotoxin- and pathogen-induced brain damage, and accumulation of neurotoxic β-amyloid. In this inflammatory theory of Alzheimer’s disease, β-amyloid—a known antimicrobial protein—accumulates in response to oral pathogens. Canine cognitive dysfunction (CCD) is considered a naturally occurring animal model of human Alzheimer’s disease. Like humans, periodontal disease is quite common in dogs; however, a link between periodontal disease and cognitive dysfunction has not been identified in this species. AIM: The purpose of this prospective investigation was to compare visual periodontal scores (from digital oral photographs) with numerical (0–54) cognitive assessment questionnaire forms in aging dogs with and without a clinical diagnosis of CCD. METHODS: A visual analogue scale (0–4) was used to score the severity of periodontal disease in 21 aging dogs: 11 dogs with a clinical diagnosis of presumptive CCD and 10 dogs without a clinical history of cognitive decline. Individuals scoring the dental photographs were blinded to all case information, including cognitive assessment scores. Cognitive assessment scores were compared with periodontal disease scores for all dogs. RESULTS: There was a significant (p < 0.05) association between periodontal and cognitive scores, with higher cognitive impairment scores being more likely in dogs with more severe periodontal disease and vice versa. No associations were identified between age and either periodontal disease or cognitive impairment. CONCLUSION: Although a cause-and-effect relationship between periodontal disease and cognitive impairment cannot be ascertained from this preliminary study, we established a link between these two disorders that warrants further investigation using more stringent criteria for evaluating both periodontal disease and cognitive dysfunction.