Objective and subjective masticatory function in older individuals

Abstract

Introduction: Oral health in the older population has improved, both in Sweden and in a global perspective. Oral health that has been associated to other, more general health perspectives such as nutrition and cognition, but also presents new challenges for the dental community. Oral health is a broad construct, but it has been shown that when older patients rate different oral health related concepts, the ability to masticate food is important.

Objective: The overall aim of this thesis was to explore how to assess objective and subjective masticatory function in older individuals, their possible relationships and assocoiation to nutrition as well as cognitive functions.

Methods and results: Study I systematically investigated and identified methods that have been developed to objectively assess masticatory function, also known as masticatory performance and to rate their measurement properties. Bibliographic databases were searched, including MEDLINE, Embase, Web of Science Core Collection, Cochrane, and Cinahl. Eligible papers that satisfied predefined inclusion and exclusion criteria were appraised independently by two investigators. Four other investigators independently appraised any measurement properties of the methods according to the consensus-based standards for the selection of health measurement instruments checklist. The qualities of the measurement properties were evaluated using predefined criteria. The level of evidence was rated by using data synthesis for each MP assessment method, where the rating was a product of methodological quality and measurement properties quality. Forty-six out of 9,908 articles were appraised, and the assessment methods were categorized as comminution (n = 21), mixing ability (n = 23), or other methods (n = 2). Different measurement properties were identified, in decreasing order construct validity (n = 30), reliability (n = 22), measurement error (n = 9), criterion validity (n = 6), and responsiveness (n = 4). Study II focused on older individual’s subjective and self-perceived notion of their masticatory function, known as masticatory ability. The aim of the study was to explore what factors seem to be important for older individuals’ masticatory ability and how it impacts daily life. Qualitative methodology and in-depth interviews were used, and the design was inspired by the qualitative method Grounded Theory. The final sample consisted of twelve older participants. Three categories developed from the data; Deteriorating oral health and functional loss, Eating habits, Prosthetic rehabilitation and function. A core category named Adaptation emerged that describes how individuals successfully adapt to a decreased function and despite this develop a positive view of their masticatory ability. Study III was a retrospective longitudinal study that examined the association between reduced posterior occlusal support and cognition in different cognitive domains and whether poor masticatory function increased the risk of dementia. Data came from a population–based study with up to 22 years of follow-up of 544 cognitively intact adults aged ≥50. Cognitive domains were assessed at baseline and at follow-ups and masticatory function was assessed using the Eichner Index and categorized according to the number of posterior occlusal zones. At baseline, 147 (27.0%) participants were placed in Eichner category A, 169 (31.1%) in B and 228 (41.9%) in C. After the age of 65, participants in Eichner category B and C showed an accelerated decline in spatial/fluid abilities. Eichner categories B or C were not associated with an increased risk of dementia, compared to category A. In study IV a group of 355 individuals with care dependency and functional limitations, aged 60 and older were included. By home visits, the participants underwent an oral examination and answered chewing related questions. Nutritional status was assessed using the Mini Nutritional Assessment. A total of 196 individuals met the age requirement. Of these, 86 subjects were able to answer the questions. The study did not report any concluding significant associations between the subdomains of masticatory function or the nutritional variables.

Conclusion: Methods to assess masticatory performance are often labor intensive and not fitted to a clinical setting. Further research is needed to find masticatory measurement methods, that are useful both in clinical contexts and research. Older individuals with at deteriorating oral function tend to overrate their masticatory ability and self-reported questionnaires seem less useful. With the chosen instruments in this thesis, a low number of occluding contacts was not associated to an increased risk of dementia or nutritional variables.