Immigration timing modifies the association between medication non-adherence and cognitive function in older adults.

BACKGROUND: The aging U.S. immigrant population exhibits higher rates of dementia than U.S.-born residents, yet traditional diagnostic methods often fail to detect decline due to cultural and linguistic barriers. Unintentional medication non-adherence (MNA) may serve as an early, noninvasive marker of cognitive decline, but little is known about how immigration timing and other modifiers shape this relationship.

METHODS: We analyzed data from 10,854 participants aged ≥65 years in the Health and Retirement Study (2012-2016). Cognitive function was assessed using standardized latent cognitive scores. Immigration status was classified as U.S.-born or immigrant, with immigrants further stratified by age at arrival (child/adolescent, early, middle, and late adulthood). Unintentional and intentional MNA were investigated separately, and a moderated moderation regression on cognitive function tested interactions between unintentional MNA, immigration status/timing, and education adjusted for demographic, socioeconomic, and health covariates.

RESULTS: Unintentional MNA, being an immigrant (compared to non-immigrants), and older age at immigration were associated with lower cognitive scores, while higher education was protective. Significant two-way interactions indicated that immigration status (β = -0.38 ± 0.14, p = 0.0006), timing (β = -0.13 ± 0.03, p < 0.0001), and education (β = -0.09 ± 0.03, p = 0.003) moderated the MNA-cognition association, though three-way interaction was not significant. Subgroup analysis showed that unintentional MNA was generally linked to poorer cognition, but the moderating roles of immigration timing and education varied across ethnicity-immigration subgroups. The potential for residual confounding and other study limitations should be considered when interpreting these results.

CONCLUSION: In conclusion, unintentional MNA is a sensitive marker of cognitive decline, with risk magnified among immigrants who arrived in middle-late adulthood. Integrating adherence and immigration history into clinical assessments may improve early identification and guide targeted interventions for diverse older adults.