Factors Associated with Self-Reported Oral Dryness in Community-Dwelling Adults: Focusing on the Oral Mucosal Moisture Index and Age Group

Purpose: Objective oral-moisture measures and subjective dry-mouth complaints often diverge in older adults. This study examined factors associated with self-reported oral dryness, focusing on the oral mucosal moisture index (OMMI) and age group.Methods: In this cross-sectional secondary analysis, OMMI was measured at the tongue-dorsum midline (mean of three readings) with an oral moisture-checking device (Mucus; Life Co. Ltd., Saitama, Japan) in 54 older (≥65 years) and 31 younger (20-47 years) community-dwelling adults. Self-reported dry mouth (single yes/no item), sex, denture use, and smoking were surveyed. Univariable and multivariable logistic regression examined factors associated with dry mouth; the adjusted model included OMMI and age group (events per variable = 11.5).Results: Between older and younger adults, mean OMMI did not differ (27.02 vs. 26.83; p = 0.561), and dryness was reported by 33.3% vs. 16.1% (p = 0.128). Lower OMMI was associated with higher odds of dryness (adjusted odds ratio [OR], 0.39; 95% confidence interval [CI], 0.23-0.65; p < 0.001). After adjustment for OMMI, the older group showed higher odds of reporting dryness (adjusted OR, 4.55; 95% CI, 1.21-17.16; p = 0.025; Nagelkerke R² = 0.319; area under the curve, 0.797). Sex, denture use, and smoking showed no association.Conclusion: Objective surface moisture alone does not fully explain subjective dryness; age group was also associated, although the wide CI and cross-sectional design preclude causal inference. Subjective complaints in older adults may warrant attention even when objective values appear normal, supporting joint consideration of age and symptoms in oral-frailty screening.