Apathy and depression in mild cognitive impairment: distinct longitudinal trajectories and clinical outcomes

ABSTRACT Objectives: Apathy is a common symptom in mild cognitive impairment (MCI) and may predict progression to dementia. Little research, however, has investigated the longitudinal trajectory of apathy in patients with MCI or controlled for depression, which can mimic apathy, when examining its clinical correlates. The current study sought to address these issues. Design: A prospective longitudinal study was conducted over 3 years. Setting: Nine memory clinics around Australia Participants: One hundred and eighty-five patients with MCI at baseline. Measurements: Measures of cognition, function, neuropsychiatric symptoms, caregiver burden, and medication use were completed annually with additional assessments at 3 and 6 months. Patients were also assessed for dementia by expert clinicians at these time points. Results: Of 164 patients who completed measures of neuropsychiatric symptoms, 59 (36.0%) had apathy and 61 (37.2%) had depression. The proportion affected by apathy and overall apathy scores increased over time, in contrast to measures of depression, which remained relatively stable. Apathy was associated with incident dementia and worse cognition, function, neuropsychiatric symptoms, and caregiver burden independent of both depression and incident dementia. Depression was associated with worse function, albeit to lesser degree than apathy, and neuropsychiatric symptoms. Conclusions: Apathy increases in MCI and is associated with worse clinical outcomes. These findings provide further evidence for apathy as a marker of clinical decline in older people and poorer outcomes across neurocognitive disorders.