Why Do They Just Sit? Apathy as a Core Symptom of Alzheimer Disease

Objective: Apathy is common in Alzheimer disease (AD) and has a far-reaching impact on patients’ clinical course and management needs. However, it is unclear if apathy is an integral component of AD or a manifestation of depression in cognitive decline. This study aims to examine interrelationships between apathy, depression, and function. Methods: This was a cross-sectional study of well-characterized AD patients in the National Alzheimer's Coordinating Center Uniform Data Set with a Clinical Dementia Rating (CDR) between 0.5 and 2. Participants’ function was measured using the Functional Assessment Questionnaire. Apathy and depression were measured using clinician judgment and informant-reported Neuropsychiatric Inventory–Questionnaire. Dementia severity was categorized by CDR. Results: Sample included 7,679 participants (55.7% men) with a mean (standard deviation) age of 74.9 (9.7) years; 3,197 (41.6%) had apathy based on clinician judgment. Among those with apathy, approximately half had no depression. Presence of apathy was associated with 21%, 10%, and 3% worsening in function compared with those without apathy in CDR 0.5, 1, and 2 groups, respectively. Depression was not independently associated with functional status. Results revealed no interaction between apathy and depression. Conclusion: Apathy, but not depression, was significantly associated with worse function, with the strongest effects in mild dementia. Results emphasize the need for separate assessments of apathy and depression in the evaluation and treatment of patients with dementia. Understanding their independent effects on function will help identify patients who may benefit from more targeted management strategies.