A DEPRESSIVE SUBGROUP OF MILD COGNITIVE IMPAIRMENT

Purpose: Late life depression is a risk factor for Mild Cognitive Impairment (MCI) and Alzheimer's Disease (AD). MCI represents a transitional period between normal aging and AD and, therefore, represents a potential entry point for preventing AD. Depression is a risk factor for MCI and AD; however, identifying which MCI patients suffer depression-related cognitive impairment remains difficult. The current study sought to identify a clinically-defined depressed sub group among patients with MCI Methods: Data was analyzed from 519 participants (112 MCI) from Project FRONTIER, an ongoing epidemiological study of factors impacting rural aging and health. Depression was assessed with GDS30 and cognition was assessed using the EXIT 25 and RBANS. The sample was randomly split into the training and test sample. Five GDS items were identified in the training sample that were significantly associated with MCI status and were used to create the depressive endophenotype (DepE) of MCI. In the test sample, linear regression was used to examine the impact of depression on neuropsychological tests performance, and logistic regression was conducted to examine the risk of being diagnosed with MCI. Results: In the test sample, DepE was negatively related to RBANS scores of Immediate Memory (B=-2.22, p<0.001), Visuospatial (B=-1.11, p<0.001), Language (B=-1.03, p<0.001), Attention (B=-2.56, p<0.001), and Delayed Memory (B=-1.54, p<0.001), and higher DepE scores were related to poorer executive functioning (EXIT25; B=0.65, p=0.001). DepE scores significantly increased risk for MCI ([OR]= 2.04; 95% CI=l.54-2.69). Conclusions: These findings suggest that a depressed subgroup of MCI exists. Higher DepE scores increased risk for MCI and increased risk for poorer neuropsychological functioning across a range of domains. The DepE may identify those MCI patients who experience depression-related cognitive dysfunction, thereby detecting a selective group that may benefit from depression treatment for prevention of AD.