Abstract
OBJECTIVES: Multiple chronic conditions (multimorbidity)-somatic, mental, and oral-are prevalent among old adults. However, it remains unclear how mental and oral health conditions, alongside somatic conditions, jointly contribute to cognitive trajectories. This study investigates how clinically informed multimorbidity groups, based on the presence or absence of mental and oral health conditions, are associated with cognitive function and decline among middle-aged and older US adults with somatic condition(s). DESIGN: Longitudinal cohort study. SETTING AND PARTICIPANTS: A total of 14,387 adults aged ≥50 years with at least 1 somatic condition and 2 waves of cognitive data. METHODS: Data were from the US Health and Retirement Study (2012-2018). Cognitive function was assessed using a 27-point modified Telephone Interview for Cognitive Status. Participants were classified into 4 multimorbidity groups: Somatic-Only (59.0%), Mental-Somatic (25.3%), Edentulous-Somatic (9.5%), and Edentulous-Mental-Somatic (6.3%). Generalized estimating equations analyzed group differences in baseline cognitive function and rates of cognitive decline, adjusting for sociodemographic and health-related covariates. RESULTS: Compared with the Somatic-Only group, the Mental-Somatic group had lower baseline cognition (β = -0.19, 95% CI: -0.27, -0.11) without significant differences in cognitive decline. The Edentulous-Mental-Somatic group showed significantly lower baseline cognition (β = -0.44, 95% CI: -0.61, -0.27). Both the Edentulous-Somatic (β = -0.02, 95% CI: -0.03, -0.01) and Edentulous-Mental-Somatic (β = -0.03, 95% CI: -0.02, -0.002) groups experienced accelerated decline compared with the Somatic-Only group. CONCLUSIONS AND IMPLICATIONS: Multimorbidity involving mental and oral health conditions differentially influence longitudinal cognitive function. These findings highlight the importance of moving beyond somatic-focused frameworks toward more integrated approaches in dementia prevention.