Lower cognitive function attenuates the convergence between self‐ratings and observer ratings of depressive symptoms in late‐life cognitive impairment

OBJECTIVES: Assessment of depressive symptoms in older adults is challenging especially in the presence of risks in cognitive impairment. We aimed to examine whether the convergence between two measures of depressive symptoms (self‐report and observer ratings) is affected by varying levels of cognitive function in older adults. METHODS: Self‐reported scale of depression, informant‐based rating of affective symptoms, and global cognitive function were assessed in 2533 older adults with no impairment, mild cognitive impairment, and Alzheimer's disease. The strength of rank‐order correlation between the Geriatric Depression Scale (GDS) and behavioral ratings of the Neuropsychiatric Inventory (NPI) was examined as the metric of convergent validity. RESULTS: The results showed that the strength of convergence between the two measurements gradually decreased as a function of lowered cognitive function. Overall tendency showed that diagnoses of cognitive impairment and lower levels of cognitive function were associated with lower correspondence between the two depression measurements. The loss of convergent validity is especially evident in the behavioral symptom of apathy. CONCLUSIONS: Utilizing self‐report scales of depression in older adults requires a cautious approach even with minimal or mild levels of cognitive impairment.