Salivary Flow Rate and Masticatory Performance in Relation to Functional Dependency in Older Adults: Potential Modification by Depressive Symptoms.

PURPOSE: To assess the individual and combined associations of salivary flow rate and masticatory performance with instrumental activities of daily living (IADL) impairment in community-dwelling older adults, and investigate whether depressive symptoms modified these associations. METHODS: This cross-sectional study used baseline data from an ongoing prospective cohort study of 244 community-dwelling older adults in Yangon, Myanmar. IADL impairment was defined as a Lawton IADL scale score of ≤ 7. Low salivary flow rate was defined as < 0.1 mL/min and poor masticatory performance as a xylitol chewing gum score of ≤ 3. Participants were classified into four groups based on these two measures. Depressive symptoms were assessed using the Geriatric Depression Scale-15 (score ≥ 5). Multivariable binary logistic regression, interaction terms, and stratified analyses were conducted. RESULTS: The prevalences of IADL impairment and depressive symptoms were 46.3% and 50.4%. Low salivary flow rate was independently associated with IADL impairment after adjustment (aOR: 1.89, 95% CI: 1.08-3.28), while poor masticatory performance alone was not. In the combined four-group model, participants with any oral impairment had higher odds of IADL impairment compared with those with normal salivary flow rate and masticatory performance. In stratified analyses, the association between low salivary flow rate and IADL impairment was more apparent among participants with depressive symptoms (aOR: 2.04, 95% CI: 1.09-4.47). CONCLUSION: Low salivary flow rate was associated with IADL impairment in community-dwelling older adults. The association appeared more pronounced among those with depressive symptoms, but this potential modifying role requires confirmation in larger longitudinal studies.