Unique effects of apathy and depression signs on cognition and function in amnestic mild cognitive impairment

Apathy and depression are the most common neuropsychiatric features in mild cognitive impairment (MCI). These syndromes have been linked to cognitive and functional decline. This study aimed to examine their unique relationships with specific cognitive abilities and daily functioning among MCI patients with memory impairment (amnestic MCI).

Data from 90 individuals referred for outpatient clinical neuropsychological evaluation and subsequently characterized as having amnestic MCI were obtained from a memory disorders center. MCI was defined using current NIA-Alzheimer's Association criteria. Variables included caregiver-reported apathy (Frontal Systems Behavior Scale) and depression (Memory and Behavioral Problems Checklist), scores on neuropsychological measures, and the Lawton-Brody Instrumental Activities of Daily Living Scale. Data were analyzed with multiple regressions controlling for age and education.

Depression was independently associated with composite scores of executive functioning. Neither apathy nor depression was associated with composite scores of attention, memory, or language. With regard to individual measures of executive functioning, depression was independently associated with poorer set-shifting (i.e., Trails B). Apathy was independently associated with poorer letter fluency (i.e., FAS). Apathy, but not depression, was associated with greater functional impairment.

Apathy and depression are associated with different aspects of executive functioning in amnestic MCI, which may reflect differing patterns of frontal lobe pathology. Apathy exerts a greater impact on daily functioning than depression and may therefore increase reliance on caregivers. Results support the separability of apathy and depression in amnestic MCI. Clinicians should differentiate these neuropsychiatric states during assessment and treatment.