Association between oral health and frailty

Student thesis: Doctoral ThesisDoctor of Philosophy


Background: The demographic transition in the past few decades led to a rapid increase in the ageing populations around the world. One of the most profound public health implications of the ageing population is frailty. Frailty is characterized by a decline in the function across physiological systems and an increase of vulnerability against stressors. Furthermore, it is associated with many adverse health outcomes and exerts financial burdens on healthcare systems. The mechanism of frailty development is a multifactorial dynamic process, oral health could be associated with frailty through different pathways. One of the most plausible pathways is the impact of poor oral health on nutritional status. Aim: The aim of the thesis was to explore the interrelationship between oral health and frailty using frailty phenotype and frailty index and the role of nutrition among older adults. The objectives of the thesis were to examine the association between the number of teeth, periodontal disease, self-rated oral health and frailty, and to assess whether nutritional status and nutritional intake mediate this association. Methods: For the primary data in Saudi Arabia, frailty was measured with the frailty phenotype and the frailty index. Oral health included the following measures: self-rated oral health, number of teeth, functional dentition, use of dentures, dry mouth symptoms and functional teeth units. Nutritional status was assessed with mini-nutritional assessment short form. For the secondary data analysis, data from NHANES 2011-2014 and 2015-2018 were used. Frailty was measured with frailty index. Oral health indicators included number of teeth, self-rated oral health and periodontal disease. A composite nutritional intake variable based on 13 micronutrients was used in NHANES 2011-2014, and the nutritional index was constructed in NHANES 2015- 2018. Logistic regression and negative binomial regression models were constructed to test the association between oral health indicators and frailty adjusting for the demographic, socioeconomic factors and nutritional status indicators. For NHANES 2015-2018, a path analysis using the structured equation modelling was conducted to estimate total effect, direct effect, and indirect effect (through nutritional index) of number of teeth on frailty index adjusted for age and gender. Results: Oral health indicators showed different significant associations with frailty. Adjusting for nutritional status indicators attenuated these associations. For the primary data collected in Saudi Arabia, 362 older adults (60 year-olds) participated in the study (response rate: 86%). Functional dentition was associated with frailty phenotype, in the fully adjusted model, Odds Ratio (OR) = 0.36 (95% CI: 0.13, 0.56). Denture use, and the number of dry mouth symptoms were significantly associated with frailty phenotype in the fully adjusted model which included nutritional status. Oral health indicators showed stronger associations with frailty index compared to frailty phenotype. For each additional tooth, the Rate Ratio (RR) for frailty index was 0.99 (95% CI: 0.98, 0.99) in the fully adjusted model. Other oral health indicators including functional dentition, denture use, self-rated oral health, and dry mouth symptoms were significantly associated with frailty index in the first model and after adjusting for the nutritional status in the second model. Using NHANES 2011-2014 data, objective oral health indicators -apart from periodontal disease- showed strong associations with frailty index, as the number of teeth, and functional dentition were significantly associated with frailty index after adjusting for the inadequate nutritional intake and in the fully adjusted model. For each tooth present in the mouth, the rate ratio of a point increase in the frailty index was 0.99 (95% CI: 0.98, 0.99) in the fully adjusted model. A dose-response association was observed between self-rated oral health and frailty index as worse self-rated oral health had higher rates of the frailty index. In NHANES 2015-2018 data, using the path analysis, number of teeth, nutritional index and age were significantly associated with the frailty index score. A higher number of teeth was related to a lower frailty index score (standardized coefficient = – 0.26, 95 CI: - 0.33, - 0.19), whereas the increase in the nutritional index was related to higher frailty index scores (standardized coefficient = 13.7, 95 CI: 9.9, 17.4). The indirect effect of number of teeth on the frailty index through nutritional index was statistically significant (standardized indirect coefficient = –0.04, 95 CI: -0.05, -0.02). Conclusion: This study illustrated that oral health is associated with frailty, and nutritional status indicators appeared to mediate the association. It also demonstrated that periodontal disease has a relatively weaker association with frailty index. Furthermore, it highlighted that poorer selfrated oral health is associated with higher rates of frailty index. It also highlighted the importance of maintaining good oral health at older age and incorporating indicators of oral health in routine geriatric assessments and health surveys. Future longitudinal studies assessing the association between oral health and frailty should consider using the frailty index, as it reflects a comprehensive geriatric status and is more sensitive to changes in clinical and laboratory assessments. Future research should also assess the role of potential mediating factors such as the inflammatory pathway for this association.
Date of Award1 Sept 2021
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorWael Sabbah (Supervisor) & Eduardo Bernabe (Supervisor)

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