In this prospective cohort study of older participants representing the general rural population of Korea, a worsening self-reported state of oral health was associated with deteriorating geriatric clinical parameters at 2 years and adversely affected the composite outcome of death and institutionalization. However, these associations were attenuated after adjusting for demographic and geriatric parameters. While most previous studies assessed oral health status as a predictor of future undernutrition in older adults, this study comprehensively evaluated the interaction between oral health status at baseline and for future geriatric functional parameters.
In our study, individuals with poor self-reported oral health were more likely to be malnourished and sarcopenic, consistent with literature supporting the importance of oral health parameters such as the number of teeth, salivary secretion, and masticatory ability in maintaining essential daily nutrition . Individuals with poor oral health have difficulty in chewing vegetables, fruit, and meat  and thus, may consume comparatively easy-to-swallow but less nutritious food such as mashed or blended foods with high sugar or fat content [1, 9, 28, 29]. Moreover, in our study, participants with poor oral health had a higher rate of baseline multimorbidity, consistent with previous studies supporting the association of poor oral condition with systemic diseases including diabetes, cardiovascular disease, pulmonary infection, kidney disease, and even dementia [30–34]. Possible explanations for these associations include systemic inflammatory responses due to periodontitis or oral abscess causing comorbidity, and the fact that oral disease and comorbidities share risk factors such as alcohol, smoking, and unhealthy diet . Unsatisfactory oral health also can adversely affect mood, as observed in the present study. Individuals tend to be socially withdrawn when feeling embarrassed to eat or communicate with others due to inaccurate pronunciation or aesthetic appearance from a lack of teeth . These factors may negatively affect mental health, lower self-esteem, and cause depression [36, 37].
In addition to these cross-sectional associations of oral health and geriatric parameters, we also observed the longitudinal impacts of baseline oral health on the future incidence of geriatric syndromes and composite outcome, although the impacts of oral health status on the incidences of the clinical outcomes were attenuated by including baseline geriatric parameters. Frailty, a clinically recognizable state of vulnerability with decreased physiological reserve occurring with human aging, is associated with falls, disabilities, treatment-related adverse outcomes, and even mortality . The risk factors for frailty and frailty progression include socio-demographic, physical, biological, psychological, and lifestyle factors [39, 40]. Because oral health influences physical (weight and muscle loss, disability, and mobility), biological (inflammation), psychological (depression and cognition), and lifestyle (food intake) factors, these various conditions and oral health itself may lead to longitudinal deterioration of frailty, resulting multifaceted deterioration across geriatric parameters. With previously reported evidence suggesting frailty as an aging phenomenon correlated with global functional parameters [16, 41], our observation of attenuation with baseline parameters as co-variables suggests close interactions between oral health, frailty, and geriatric syndromes.
We used three self-reported items to evaluate oral health. In resource-limited, real-world clinical practices, the use of comprehensive oral health assessments might be less feasible. We selected these three items to reflect the various facets of oral health including physical function in speaking (item 1), pain and discomfort (item 2), and psychosocial/psychological aspects (item 3) . These limited items captured the cross-sectional correlations and longitudinal clinical relevance of baseline oral health status, suggesting the possible clinical benefits of brief oral assessments in caring for geriatric populations.
Recent reports indicate that frailty and geriatric syndromes can be managed even in resource-scarce rural communities through the applicate of multicomponent intervention programs including exercise; nutrition; and geriatric management of potentially inappropriate medications, chronic diseases, cognitive- and mood problems [42, 43]. The combination of the observations from the present study with those of previous reports allows the future assessment of the beneficial effects of community-based programs targeting older populations to improve oral health status on frailty and geriatric outcomes on top of dental health status per se.
Our study has some limitations. First, our study population was limited to a rural country of South Korea. Therefore, our results may not be generalized to other regions and ethnicities, although previous reports from the same population showed comparable characteristics to those in Korean rural-dwelling older populations . Second, medically objective oral health evaluations were not performed. Further studies are warranted that include physician-assessed oral health, with some interventional attempts to assess the possible protective effects of dental care in older populations to improve geriatric outcomes. Third, while the statistical associations between oral health status and incidence of geriatric syndromes or the composite outcome were attenuated in multivariate analysis, positive trends for worsening baseline oral health toward increased likelihoods of the negative outcomes were observed. Because the independent impact of oral health on geriatric outcomes could not be confirmed in our cohort, future studies in larger populations might be informative.