Cognitive Decline or Periodontists – Which Comes First?

Recent research suggests the isolated belief that cognitive decline primarily comes before periodontitis hinders our full understanding of how dementia and periodontitis relate.

By Genni Burkhart

The number of people living with dementia worldwide is estimated to be over 55 million. By 2050 it's estimated that number will reach 139 million people globally.

Dementia is a general term used to describe the various brain disorders that affect memory, emotions, and behavior – with Alzheimer's disease (AD) being the most common cause of dementia.

In September, a meta-analysis published in the Journal of the American Geriatrics Society indicated a connection between dementia and periodontitis with tooth loss.

We'll discuss some of the interesting findings of these studies and if there's any further indication on which comes first – dementia or periodontitis.

Converse or Directional Relationship?

The traditional thinking is that due to dementia, poor oral hygiene is likely to occur, increasing the risk of periodontitis and tooth loss. However, in the article, "Periodontitis and Dementia: A Bidirectional Relationship?" 1 published in the Journal of Dental Research, authors suggest this belief (dementia first, periodontitis later) hinders our complete understanding of how AD and periodontitis relate.

Citing a growing body of literature (Stein et al., 2007; Sparks Stein et al., 2012; Farhad et al., 2014; Demmer et al., 2020; Nadim et al., 2020) (1) the study further suggests that periodontal disease can precede AD-associated dementia and that a converse relationship, not simply a bidirectional one exists.

Various studies are mentioned in the article, "Periodontitis and Dementia: A Bidirectional Relationship?" 1 published in the Journal of Dental Research, showing multiple relationships.

A bidirectional relationship was mainly associated with younger patients with AD (<60 y) and in the 61- to 70-y cohort with AD, which are more likely to experience a longer duration of dementia. A bidirectional relationship also appears in the higher age group (>80 y) with AD but with less severity of periodontal disease.

A history of poor oral hygiene is associated with exacerbating early-onset AD and rapid deterioration in cognition due to inflammation following periodontal disease, casually relating periodontal disease and AD. Ma et al. (2021) However, human pathophysiology and an individual's lifestyle, genes, and environmental influences determine causality in studies on oral-systemic cognitive diseases (Raittio & Farmer, 2021) and oral-chronic cognitive diseases such as AD-associated dementia is complex. Therefore, reaching this simplistic conclusion isn't conclusive. Research suggests that periodontal disease and AD-associated dementia may be related/dependent on each other, but further research is required to clarify the direction of this relationship.

Tooth Loss

According to the meta-analysis published in the Journal of the American Geriatrics Society, gum disease and tooth loss may be associated with cognitive decline and dementia in later life. A total of 24 longitudinal studies examined the relationship between periodontitis and cognitive decline, while 23 others assessed the association between periodontitis and dementia.

There was a 23 percent higher risk of cognitive decline and a 21 percent higher risk of dementia associated with poor periodontal health (such as periodontitis, tooth loss, deep pocketing, and alveolar bone loss).

The meta-analysis found that periodontitis was associated with increased cognitive decline and dementia risk. Further analyses revealed that tooth loss was independently linked to cognitive decline and dementia among the various criteria for assessing periodontitis.

Cognitive decline was associated with partial tooth loss. However, partial tooth loss was not linked to dementia, but complete tooth loss was.

In Conclusion

As the study (2) authors state: "From a clinical perspective, our findings emphasize the importance of monitoring and management of periodontal health in the context of dementia prevention, although the available evidence is not yet sufficient to point out clear ways for early identification of at-risk individuals, and the most efficient measures to prevent cognitive deterioration."

These studies are just small pieces in the larger fight against dementia and AD. However, the results are essential in understanding the cause of the cognitive decline and its relationship to gum disease. The hope is that further treatment will come from these studies' increased understanding.


  1. Harding A, Singhrao SK. Periodontitis and Dementia: A Bidirectional Relationship? Journal of Dental Research. 2022;101(3):245-246. doi:10.1177/00220345211043461
  2. Asher, S, Stephen, R, Mäntylä, P, Suominen, AL, Solomon, A. Periodontal health, cognitive decline, and dementia: A systematic review and meta-analysis of longitudinal studies. J Am Geriatr Soc. 2022; 70( 9): 2695- 2709. doi:10.1111/jgs.17978

Author: With over 12 years as a published journalist, editor, and writer Genni Burkhart's career has spanned politics, healthcare, law, business finance, technology, and news. She resides on the western shores of the idyllic Puget Sound where she works as the Editor in Chief for the Incisor at DOCS Education out of Seattle, WA.

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