Poor periodontal health negatively impacts cognition, according to a noteworthy review that was published on September 9 in the Journal of the American Geriatrics Society that analyzed existing evidence concerning the effect of poor periodontal health on cognitive decline and dementia.
A total of 47 studies were included in the review: 24 for cognitive decline and 23 for dementia. In the literature, poor periodontal health was reflected as periodontitis, tooth loss, deep periodontal pockets, and alveolar bone loss. Poor periodontal health was associated with both cognitive decline and dementia.
"Poor periodontal health, overall tooth loss, and complete tooth loss were associated with dementia; poor periodontal health, overall tooth loss, and partial tooth loss were associated with cognitive decline," wrote the study authors, led by Sam Asher, MPH, of the University of Eastern Finland.
Further, the analysis showed that tooth loss independently increased the risk of both cognitive decline and dementia. Complete tooth loss was more commonly associated with dementia, while partial tooth loss was more commonly associated with cognitive decline. However, the quality of evidence was low, and the findings were at least partly due to reverse causality.
Dementia studies with more than 10 years of follow-up showed a weakening effect of poor periodontal health on dementia compared to the main analysis, with estimates for tooth loss becoming insignificant. This indicates that part of the associations observed in the main analysis was due to reverse causality.
Since neuropathological and cognitive changes develop over time, a study duration of less than 10 years is unlikely to remove the potential effects of cognitive impairment on periodontal health.
In an additional meta-analysis that was conducted that excluded studies where dementia and cognitive statuses at baseline were unclear, poor periodontal health had stronger associations with cognitive decline across all measures of poor periodontal health, including overall tooth loss, complete tooth loss, and partial tooth loss.
Researchers speculate that this finding may have two explanations: Periodontal health may be a risk factor for multiple types and varying severities of cognitive decline, not just dementia. However, the stronger associations may still reflect reverse causality, since participants with dementia at follow-ups were not excluded from the studies, and shorter follow-ups predispose them to the effects of reverse causality.
The pattern of stronger associations with shorter study durations has been described for other risk factors for cognitive decline and dementia, like depression.
"Our findings emphasize the crucial need for improving the design of periodontal-cognitive health studies, with particular focus on sufficient follow-up time and thorough data analytical consideration of cognitive impairment and dementia status at both baseline and follow-up visits," the study authors wrote.
From a clinical perspective, the findings highlight the importance of monitoring and managing periodontal health within the context of dementia prevention. However, there is not yet sufficient evidence to suggest clear ways for early identification and the most efficient preventative measures.
"Further well-designed studies involving standardized periodontal and cognitive health assessment and addressing reverse causality are highly warranted," Asher and colleagues concluded.