Self‐reported and informant‐reported depressive symptoms are independent and divergent predictors of new onset dementia in older adults

Abstract

Background: Depressive symptoms in older adults are important predictors of incident dementia. Symptoms can be assessed in several ways, including self-reported or informant-reported measures. It is unclear whether one is superior in predicting dementia onset or how to interpret discordant reports. Here, in a large sample of nondementia older adults for whom depressive symptoms were assessed via both selfreport and informant-report, we test independent and divergent prognostic utility for dementia.Method: Data from 10,684 non-dementia subjects from the National Alzheimer's Coordinating Centre were analysed. This included individuals with normal cognition (NC; CDR=0) and Mild Cognitive Impairment (MCI; CDR=0.5). Geriatric Depression Scale-15 (GDS) was used for self-report and the Neuropsychiatric Inventory Questionnaire depression item (NPI-Q-D) was used for informant-report. Cox regression and Kaplan Meier (KM) survival analyses were used to explore the measures as independent predictors of dementia, and the putative interaction between them. Outcome was defined as change to CDR≥1 at follow-up. The cox model was adjusted for age, sex, and education. CDR category was included to determine applicability of findings across cognitive categories. GDS-15 and NPI-Q-D scores were added as continuous predictors. For the KM analysis, depressive symptoms were dichotomized as GDS+/GDSand NPI-Q-D+/NPI-Q-D-using cut-off scores of ≥5 for GDS-15 and ≥2 for NPI-Q-Depression.