Distinguishing apathy and depression in dementia: A longitudinal study.

Objectives: Apathy is a common symptom in dementia, though can be difficult to distinguish from depression due to shared features and frequent co-occurrence. As such, a significant limitation of much previous research on apathy is the failure to control for depression. The current study sought to address this by examining the trajectory and clinical correlates of apathy after controlling for depression.

Methods: Seven hundred and seventy-nine patients with dementia were recruited from nine memory clinics around Australia. Measures of dementia severity, cognition, functional ability, neuropsychiatric symptoms, caregiver burden and medication use were completed at baseline and at regular intervals over a 3-year period. Driving and institutionalisation data were obtained throughout the study. Mortality data were obtained from state registries 8 years after baseline.

Results: Of the 662 patients with completed measures of neuropsychiatric symptoms, 342 (51.7%) had apathy and 332 (50.2%) had depression at baseline, while 212 (32.0%) had both. Whereas apathy increased over time, depression remained relatively stable. Apathy, but not depression, was associated with greater dementia severity, poorer cognition and function, driving cessation and mortality. Both apathy and depression were associated with greater neuropsychiatric symptoms, psychosis, caregiver burden and institutionalisation.

Conclusions: Apathy increases over the course of dementia and is associated with worse clinical outcomes independent of depression. Distinguishing apathy and depression appears important given their different implications for prognosis and management.