Periodontitis not linked to cognitive decline but tooth retention may prevent cognitive impairment: Study

A new study published in the Journal of Alzheimer’s Disease revealed that clinical periodontitis was not linked to the onset of dementia or mild cognitive impairment (MCI), whereas tooth retention showed a protective association. Elevated inflammatory markers in affected men suggest that systemic inflammation may play a role in cognitive decline.

Periodontitis is a bacterial infection that triggers long-term inflammation in the gums, and previous retrospective studies have linked oral bacteria to brain pathology. However, few studies have combined detailed dental exams, cognitive assessments, and inflammatory blood markers over time. Researchers from the PRIME-COG cohort followed 642 men for an average of nearly 16 years to examine whether periodontitis increased the risk of developing mild cognitive impairment (MCI) or dementia.

The study’s main finding investigated the baseline clinical periodontitis and its association with later development of MCI or dementia. Men with severe gum disease were no more likely to develop cognitive impairment than those with mild or no disease. This result held even after adjusting for potential confounders in statistical models.

Each additional tooth was associated with a lower risk of developing dementia or MCI. The men who retained more of their natural teeth over time were better protected against cognitive decline. This finding points toward tooth loss as a potential marker of long-term health vulnerability, rather than gum disease severity alone.

Men who went on to develop dementia or MCI already showed higher levels of inflammatory markers at the study’s outset, including interleukin-6 (IL-6), interleukin-8 (IL-8), and interferon-gamma (IFN-γ). At follow-up, elevated IL-8 and transforming growth factor-beta (TGF-β) were still evident, which suggested a persistent inflammatory state.

Another key aspect of the research involved immune responses to periodontal bacteria. Blood levels of IgG antibodies against common periodontal pathogens remained stable over time in men who developed cognitive impairment, while these antibody levels declined in men who remained cognitively healthy.

Also, in the group that developed dementia or MCI, higher antibody levels were positively correlated with proinflammatory cytokines, reinforcing the link between immune activation and systemic inflammation. Overall, the findings suggest that maintaining teeth and managing systemic inflammation may be more relevant to cognitive health than gum disease severity alone, and this insight could reshape future research into dementia prevention.

Source:

Farsi, D. N., Abadalkareem, R., Linden, G. J., McKay, G. J., McEvoy, C. T., McAlinden, M., Winning, L., Hurley, M., Kelly, J., Passmore, P. A., Holmes, C., Patterson, C. C., Teeling, J. L., & McGuinness, B. (2025). Periodontitis and incident cognitive decline and dementia: A 15-year prospective cohort study of older men residing in Northern Ireland. Journal of Alzheimer’s Disease: JAD, 13872877251401563, 13872877251401563. https://doi.org/10.1177/13872877251401563