Impact of Oral Health on Cognitive Functioning, Decline and Impairment Among Older Adults in England

Abstract

Background: Several studies have assessed the association between oral health and cognition in the elderly, although very few studies have investigated the longitudinal association in England. Different theories have been reported in the literature explaining the potential pathways between oral health and cognitive impairment, including inflammatory and nutritional factors. Additionally, social factors are a significant risk factor for cognitive impairment and are also highly correlated with oral health. Aim: This thesis aimed to examine the association between various oral health measures with cognitive functioning, change of cognitive functioning over time, and cognitive impairment in a nationally representative sample of older English adults. Additionally, the inflammatory, nutritional and social pathways were assessed. Methods: Secondary data from wave 3 (2006-07) to wave 8 (2016-17) of the English Longitudinal Study of Ageing (ELSA) were analysed. Three oral health measures were examined at baseline (wave 3) including self-reported oral health, oral impacts and edentulism. Cognitive functioning outcomes examined were memory using the word recall test and executive function using the animal naming test. Cognitive impairment was assessed at the follow-up wave 8 using the modified Telephone Interview for Cognitive Status (mTICS). Linear regression was used to assess the association with cognitive functioning cross-sectionally and longitudinally, linear mixed-effects models were used to assess the association with the change of cognitive functioning over time, and time-lag logistic regression models were used to assess the association with the subsequent cognitive impairment. Finally, several Structural Equation Models (SEM) were used to analyse the potential pathways of the association between oral health and cognitive impairment. Results: This thesis showed that edentulism significantly predicted lower memory and executive function; while self-reported oral health predicted lower memory only in the edentate sample. The thesis also showed weak evidence of oral impacts predicting memory decline, although the association was marginally non-significant in the full model. Edentulism and oral impacts were strong predictors of subsequent cognitive impairment, independent of many covariates. The association between edentulism and cognitive impairment was significantly mediated by social isolation and preceded by inflammation. Conclusion: The overall findings of this thesis highlights the importance of oral and cognitive health in a national sample of older people. The results highlight the opportunity for future research to examine the potential effect of oral health in preventing or slowing the onset of dementia.