A six-month observational study has investigated whether periodontitis is associated with dementia severity and cognitive decline in 60 subjects with mild-to-moderate Alzheimer’s disease living in the community (Raybould et al. PLoS One 2016;11:e0151081, free full text at www.ncbi.nlm.nih.gov/pmc/articles/PMC4786266/pdf/pone.0151081.pdfAbstract).

Subjects were assessed at baseline and at 6 months. The primary outcome measure was change from baseline in ADAS-cog. Blood samples were obtained for C-reactive protein (CRP) inflammatory cytokines (tumour necrosis factor-alpha, interleukin-10), and antibodies to Porphyromonas gingivalis, a Gram-negative anaerobe implicated in periodontal disease. Dental health was evaluated by a dental hygienist blinded to cognitive status.

At 6-month follow-up, the presence of periodontitis was associated with a six-fold increase in the rate of cognitive decline. The mean change from baseline in ADAS-cog score was 6.1 in patients with periodontitis versus 0.9 in patients without periodontitis. There was no clear relationship between severity of dementia and degree of periodontitis. Baseline periodontitis and P. gingivalis antibody levels were associated with a decline in IL-10 during the course of the study.

The researchers noted that the relationship between periodontitis and increased cognitive decline may be due to several factors, such as poorer dental hygiene due to worsening cognition. Periodontitis may also promote or be a reflection of an increased systemic inflammatory response, which may have an impact on cognition.

Comment
Dr. Catherine Brodeur: Inflammation has been described by some as the culprit for Alzheimer’s disease, based on different assumptions. This study would be another proof that inflammation is important in AD.  Nonetheless, we must recognize that this is a very short-term study and that many confounding factors are present.