Abstract
BACKGROUND: Little is known about how depressive symptoms and glial fibrillary acid protein (GFAP) concentrations taken together may influence cognitive functioning. Understanding this relationship may inform strategies for screening and early intervention to decrease the rate of cognitive decline. METHODS: This study sample includes 1 169 participants from the Chicago Health and Aging Project (CHAP), consisting of 60% Black participants and 40% White participants, and 63% female participants and 37% male participants. CHAP is a population-based cohort study of older adults with a mean age of 77 years. Linear mixed-effects regression models tested the main effects of depressive symptoms and GFAP concentrations and their interactions on baseline cognitive function and cognitive decline over time. Models included adjustments for age, race, sex, education, chronic medical conditions, body mass index, smoking status, alcohol use, and their interactions with time. RESULTS: The interaction of depressive symptomology and GFAP (β = -0.105 [standard error = 0.038], p = .006) on global cognitive function was statistically significant. Participants with depressive symptoms including and above the cutoff and high log of GFAP concentrations had more cognitive decline over time, followed by participants with depressive symptoms below the cutoff and high log of GFAP concentrations, depressive symptom scores including and above the cutoff and low log of GFAP concentrations, and depressive symptom scores below the cutoff and low log of GFAP concentrations. CONCLUSIONS: Depressive symptoms have an additive effect on the association between the log of GFAP and baseline global cognitive function.