Self-versus caregiver-reported apathy across neurological disorders

Apathy is a prevalent and persistent neuropsychiatric syndrome across many neurological disorders, significantly impacting on both patients and caregivers. We systematically quantified discrepancies between self- and caregiver-reported apathy in 335 patients with a variety of diagnoses, frontotemporal dementia (behavioural variant and semantic dementia subtypes), Parkinson’s disease, Parkinson’s disease dementia, dementia with Lewy bodies, Alzheimer’s disease dementia, mild cognitive impairment, small vessel cerebrovascular disease, subjective cognitive decline and autoimmune encephalitis.

Using the Apathy-Motivation Index (AMI) and its analogous caregiver version (AMI-CG), we found that caregiver-reported apathy consistently exceeded self-reported levels across all conditions. Moreover, self-reported apathy accounted for only 14.1% of the variance in caregiver ratings. This apathy reporting discrepancy was most pronounced in conditions associated with impaired insight, such as behavioural variant frontotemporal dementia, and was significantly correlated with cognitive impairment. Deficits in memory and fluency explained an additional 11.2% of the variance in caregiver-reported apathy, highlighting their crucial role in goal-directed behaviour. Specifically, executive function deficits (e.g., indexed by fluency) and memory impairments may contribute to behavioural inertia or recall of it.

These findings highlight the need to integrate patient and caregiver perspectives in apathy assessments, especially for conditions with prominent cognitive impairment. To improve diagnostic accuracy and deepen our understanding of apathy across neurological disorders, we emphasise the need of standardised apathy assessment tools tailored to individuals with cognitive deficits. Understanding the cognitive mechanisms underpinning discordant apathy reporting in dementia might help to inform targeted clinical interventions and reduce caregiver burden.