The impact of study factors in the association of periodontal disease and cognitive disorders: systematic review and meta-analysis

Abstract

Aim The aim was to assess study factors that impact the association of cognitive disorders in people with periodontal disease (PD). Method Medline, EMBASE and Cochrane databases were searched until February 2022 using keywords and MeSH: (periodon* OR tooth loss OR missing teeth) AND (dementia OR Alzheimer’s Disease OR cognitive*). Observational studies reporting prevalence or risk of cognitive decline, dementia or Alzheimer’s disease (AD) in people with PD compared with healthy controls were included. Meta-analysis quantified the prevalence and risk (relative risk[RR]) of cognitive decline, dementia/AD, respectively. Meta-regression/subgroup analysis explored the impact of study factors including PD severity and classification type, and gender. Results Overall, 39 studies were eligible for meta-analysis: 13 cross-sectional and 26 longitudinal studies. PD demonstrated increased risks of cognitive disorders (cognitive decline—RR = 1.33, 95% CI = 1.13–1.55; dementia/AD—RR = 1.22, 95% CI = 1.14–1.31). Risk of cognitive decline increased with PD severity (moderate—[RR] = 1.14, 95% confidence interval [CI] = 1.07–1.22; severe—RR = 1.25, 95% CI = 1.18–1.32). For every 10% population increase in females, the risk of cognitive decline increased by 34% (RR = 1.34, 95% CI = 1.16–1.55). Self-reported PD showed a lower risk of cognitive disorders compared with clinical classification (cognitive decline—RR = 0.77, 95% CI = 0.65–0.91; dementia/AD—RR = 0.86, 95% CI = 0.77–0.96). Conclusion The prevalence and risk estimates of cognitive disorders in association with PD can be influenced by gender, the disease classification of PD and its severity. Further homologous evidence taking these study factors into consideration is needed to form robust conclusions.

Neuroinflammation and Neurodegenerative Diseases: How Much Do We Still Not Know?

“…Data from a recent national US retrospective cohort study showed that periodontal pathogens increase the risk of AD incidence and mortality [143]. In addition, data from a recent meta-analysis showed that the risk of cognitive disorder in individuals with PeD increases as the severity of PeD increases, and this risk appears to be greater in the female sex [144]. There are at least two main mechanisms by which PeD can cause cognitive disorders.…”

“…There are at least two main mechanisms by which PeD can cause cognitive disorders. The first involves the presence of an increased cerebral inflammatory state caused by the SCI process originating from oral pathogens; the second involves a direct action of periodontal bacteria on the CNS that cross the BBB and cause its breakdown with subsequent, potential triggering of the preexisting neurodegenerative process [141][142][143][144].…”

Risk factors of cognitive impairment: Impact of decline in oral function

“…And the other is suboptimal oral health, such as gingivitis, dental caries, tooth loss, and edentulousness, appears to be associated with increased risk of developing cognitive impairment and dementia. In recent meta-analysis about the relationship between periodontal disease and cognitive disorder, risk of cognitive decline in increased with periodontal disease severity [40] . The other meta-analysis [12] showed that there are three possible mechanisms by which tooth loss leads to cognitive decline: tooth loss may reduce sensory stimulation to the brain, dental status can be linked to cognitive impairment via the nutritional pathway, and periodontal disease may play a role through neuro-inflammation.…”

Poor oral health and dementia risk under time‐varying confounding: A cohort study based on marginal structural models

“…Previous studies reported that poor cognitive function also leads to poor oral health among older adults 10–12 . A previous longitudinal study showed that the association between cognitive function and oral health was bidirectional 13 .…”

“…Previous studies reported that poor cognitive function also leads to poor oral health among older adults. [10][11][12] A previous longitudinal study showed that the association between cognitive function and oral health was bidirectional. 13 Therefore, a bidirectional association could exist between poor oral health and poor cognitive function, which in turn leads to poor oral health.…”