2025 Theses Doctoral

Examining the Relationship Between Poor Oral Health and Frailty in Individuals Aged 55 Years and Older.

Diaz Toro, Felipe Ignacio

Frailty is defined as a biological syndrome marked by reduced physiological reserve and heightened vulnerability to stressors, leading to adverse health outcomes like dependency, functional impairment, cognitive decline, and mortality. While various conditions have been associated with frailty, oral health is one of them. However, the precise relationship and the underlying pathways through which oral health conditions may be associated with frailty remain unclear. Limitations such as small sample sizes, inadequate control for confounders, inconsistent results across studies, and variations in frailty assessment methods have contributed to the inconclusiveness of this relationship.

Considering these limitations, this dissertation intends to address them by using a rigorous cohort with a robust design, which will allow for a larger sample size, appropriate confounder assessment, and the opportunity to create a practical frailty index (FI) using data from this cohort. This approach enables a comprehensive investigation of the association between clinical, functional, and microbiological oral health and frailty, both cross-sectionally and longitudinally (12 years of follow-up). Furthermore, this study aims to conduct an initial exploration of the mediating effects of inflammatory biomarkers in this relationship.Three specific aims were pursued to achieve this goal.

Firstly, a systematic review was conducted to critically summarize the existing evidence on the association between poor oral health and frailty, assessed through any frailty index instrument. Subsequently, two analytical aims were undertaken to delve into the association between oral health and frailty. The initial analytical aim comprised two parts. The first part focused on creating and validating a population frailty index score using data from the Oral Infections and Vascular Disease Epidemiology Study (INVEST).

The second part aimed to investigate, cross-sectionally, whether poor oral health independent of factors such as sex, age, occupation, educational level, marital status, and smoking is positively associated with frailty. Additionally, the study aimed to test the robustness and replicability of both the FI and the cross-sectional relationship, utilizing a smaller set of oral data from the Chilean National Health Survey conducted in 2016-2017. The second analytical aim was to explore the prospective association between oral health – assessed clinically, functionally, and microbiologically- and frailty, using the INVEST cohort with its 12 years of follow-up and repeated measures for the exposure, confounders and outcome. As a secondary aim, we explored the mediating effects of select inflammatory biomarkers in this relationship.

The systematic review identified 11 studies that investigated the relationship between oral health and frailty, utilizing the FI as an instrument for assessing frailty. All these studies were cross-sectional, and the FI employed in them encompassed a range of deficits, varying from 32 to 76 items. The most frequently incorporated constructs in the frailty index were comorbidities, cognitive impairment, activities of daily living (ADL and/or IADL), functional limitations or abilities, anthropometry, depressive symptoms, and self-reported health status. In terms of the association between oral health and frailty, the review showed that a lower number of teeth, poor self-reported oral health, and experiencing chewing or oral cavity pain were associated with an increased likelihood of frailty, as indicated by any FI. Notably, no studies reported an association between periodontal disease, cavities, use of dental prostheses, and frailty.

The second aim showed that within the U.S. population, functional oral health (assessed as the number of teeth and higher number of occlusive tooth pairs) was associated with frailty. Similarly, among the Chilean population aged 55 years and older, frailty was also associated with functional oral health (lower number of additional teeth, wearing dental prostheses, and not having a functional dentition). This study also showed that the inclusion of periodontal microbiota in the regression models improved the model’s fit, suggesting that this microbiota may play a role in the association between oral health and frailty.

Finally, the third aim showed that after 12 years of follow-up, a higher incidence of frailty was associated with functional and clinical oral health. In fact, people who exhibited a lower number of additional teeth, had less than 21 teeth, wearing complete dental prostheses, and had periodontal disease had a higher incidence of frailty. Moreover, CRP, IL-6, and TNF- exhibited small, but not statistically significant, effects as potential mediators between oral health and frailty. These findings suggest the potential for further research to explore the action of other inflammatory biomarkers and pathways through which oral health may be associated with frailty.