Validity of a Combined General and Oral Health Indicator for Vulnerability

Self-rated health (SRH) is widely used for population health monitoring but may miss oral health-related vulnerability. We examined whether combining SRH with self-rated oral health (SROH) improves identification of multidimensional vulnerability among adults aged ≥45 years.

We used 2024 Korea Community Health Survey data to create a four-category SRH-SROH indicator: good both, poor oral only, poor general only, and poor both. Survey-weighted multinomial logistic regression assessed associations with sociodemographic, behavioural, health, oral healthcare access, and community-level factors. Chewing difficulty was excluded from regression models and used as an external functional validation outcome. Incremental validity was assessed by comparing Nagelkerke R² and AUC between SRH-only and combined-indicator models. Sensitivity analyses retained the full complete-case sample and reclassified 'fair' responses as poor/unhealthy or good/healthy.

In the primary high-contrast sample, 32.6% reported poor health in both domains, 20.2% poor oral health only, 7.6% poor general health only, and 39.6% good health in both domains. The poor - both groups had higher prevalence of mobility limitation, chronic conditions, depressive symptoms, and unmet healthcare needs. Among participants with good SRH, poor SROH identified hidden vulnerability, including greater mobility limitation, unmet medical needs, and chewing difficulty. For chewing difficulty, the combined-indicator model increased Nagelkerke R² from 0.373 to 0.540 and AUC from 0.822 to 0.883. Findings were directionally robust across sensitivity analyses.

Combining SRH and SROH better identified hidden functional and care-related vulnerability than SRH alone, particularly among individuals reporting good general health. Its main value is subgroup identification for population health monitoring, not stand-alone clinical screening.

Adding a single SROH item may help identify vulnerability missed by SRH alone, but clinical screening use requires further validation.