Comorbidity Burden, Polypharmacy and Xerostomia Severity in Institutionalized Older Adults

Background and Objectives: Xerostomia is common among institutionalized older adults, but the relative contributions of comorbidity burden and medication-class burden remain incompletely clarified. This study evaluated their associations with Xerostomia Inventory (XI) severity and explored related salivary dysfunction and clinical oral health findings. Materials and Methods: We conducted a cross-sectional study of 90 institutionalized older adults in Bucharest, Romania. Xerostomia Inventory (XI) scores, a binary dry-mouth question, chairside salivary assessments, comorbidity categories, medication classes, oral mucosal findings, and complete denture retention and stability were recorded. Primary analyses used hierarchical regression and bootstrap statistical decomposition; secondary and exploratory analyses evaluated salivary concordance, medication classes, denture-related findings, and oral mucosal conditions. Results: Medication-class count remained associated with XI severity after adjustment for comorbidity burden (partial r = 0.445, p < 0.001), whereas the association between comorbidity burden and XI was no longer significant after adjustment for medication-class count (partial r = -0.063, p = 0.557). Inclusion of medication-class count increased the explained variance in XI scores (ΔR² = 0.253, p < 0.001). Bootstrap decomposition yielded similar findings, with a significant indirect estimate and a non-significant direct estimate. Among complete denture wearers, XI severity was associated with maxillary denture instability (ρ = -0.687, n = 44). Conclusions: In this cohort, medication-class burden showed the strongest association with xerostomia severity, whereas comorbidity burden was not independently associated after adjustment. Given the cross-sectional design, these findings should be interpreted as exploratory associations and support future prospective studies integrating medication review with geriatric-prosthodontic assessment.