Poor oral health conditions and cognitive decline: Studies in humans and rats.

Shuang Zhang,Xueshen Qian,Fuhua Yan,Ling Gong,Song Ge,Zezheng Wang,Fengchun Yang,Yan Ji,Gianluigi Forloni

doi:10.1371/journal.pone.0234659

Shuang Zhang, Xueshen Qian + Show 7 more

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https://doi.org/10.1371/journal.pone.0234659

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Abstract

BackgroundThe relationship between poor oral health conditions and cognitive decline is unclear.ObjectiveTo examine the association between oral health and cognition in humans and rats.MethodsIn humans: a cross-sectional study was conducted. Cognitive levels were evaluated by the Mini Mental State Examination (MMSE); oral conditions were reflected by the number of missing index teeth, bleeding on probing, and probing pocket depth (PD). In rats: a ligature-induced (Lig) periodontitis model and Aβ25-35-induced model of Alzheimer’s disease (AD) were established; tumor necrosis factor-α (TNF-α), interleukin 1 (IL-1), interleukin 6 (IL-6), and C-reactive protein levels in the hippocampus and cerebral cortex were detected.ResultsMMSE scores for the number of missing index teeth ≥ 7 group were significantly lower than those in the ≤ 6 group. A negative relationship (correlation coefficient ρ = −0.310, P = 0.002) was observed between MMSE scores and number of missing index teeth. More missing index teeth and lower education levels were independent risk factors for cognitive decline. A negative relationship (correlation coefficient ρ = −0.214, P = 0.031) was observed between MMSE scores and average PD. TNF-α and IL-6 levels in the hippocampus of the Lig+AD group were significantly higher than those of the AD group. IL-1 and IL-6 levels in the cerebral cortex of the Lig+AD group were significantly higher than those of the AD group.ConclusionPoor oral health conditions including more missing index teeth and higher average PD may be risk factors for cognitive decline. Periodontitis may increase inflammatory cytokines in rat models of AD.

Highlights

Alzheimer’s disease (AD) is an age-related chronic neurodegenerative disorder presenting with progressive cognitive decline with dementia
Cognitive levels were evaluated by the Mini Mental State Examination (MMSE); oral conditions were reflected by the number of missing index teeth, bleeding on probing, and probing pocket depth (PD)
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Summary

Introduction

Alzheimer’s disease (AD) is an age-related chronic neurodegenerative disorder presenting with progressive cognitive decline with dementia. AD is the most frequent cause of dementia among the elderly [1, 2]. Cognitive decline and AD have a high morbidity and mortality rate, and adversely affect the quality of life among elderly people. The health care costs for patients with AD impinge upon their family, but society as a whole [3]. In addition to the amyloid hypothesis [4, 5] and tau protein hypothesis [6, 7], inflammation may play an important role in the pathogenesis of AD [8] and cognitive decline [9]. The relationship between poor oral health conditions and cognitive decline is unclear. Editor: Gianluigi Forloni, Istituto Di Ricerche Farmacologiche Mario Negri, ITALY

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