Patients' self-reports on function and cognition in Alzheimer's disease are strongly influenced by their affective states: Principal component analysis of the CLIMAT scale

The Clinical Meaningfulness in Alzheimer Disease Treatment (CLIMAT) scale has been designed to capture meaningful change in clinical trial and care settings. The baseline interview assesses Alzheimer Disease (AD) symptoms on two dimensions validated in previous work: severity of impairment, with patient and informant input, and impact of impairment, with patient input. Impact addresses the perceived personal-social importance of AD symptoms. Here we report on the empirically derived factor structure underlying patient and informant reports on the CLIMAT scale items. The sample comprised 97 participants with AD enrolled in a phase IV effectiveness study of cholinesterase inhibitors (ChEI) (BC Alzheimer's Drug Therapy Initiative), mean age 76.3 (SD=8.6), mean MMSE 23.8 (SD=6.3), 53% female. The majority of informants (75%) were spouses. Baseline patient and informant interviews were rated by clinicians on items in 4 domains: social (2), functional (3), cognitive (5) and affective (2) (total items=12). We computed descriptives and performed exploratory principal component analysis (PCA) with varimax rotation, on severity ratings based on patient and informant, and impact ratings based on patient. Factor loadings>0.5 were included in the interpretation. CLIMAT severity ratings: patients and informants described loss of independence, executive functioning and memory as most affected. Patient-reported severity was lower than that reported by informants, except for depressed mood and anxiety. Based on eigenvalues>1, 3-factor solutions were selected for both patient and informant severity ratings. Patient-rating factors were social engagement- mood, cognition-anxiety, and independence-executive functioning (65%-variance explained); informant-rating factors were function-cognition, social engagement, and mood-anxiety (72%-variance explained). CLIMAT impact ratings: patients described losses in independence and memory, depressed mood and anxiety as most impactful. A 3-factor solution was selected for impact ratings, with independence-mood-anxiety, social engagement and cognition as factors (65%-variance explained). In patient but not informant reports, affective symptoms are closely linked to social, cognitive and functional symptoms of AD. This suggests that there are important differences in how patients and informants perceive, and report on AD symptoms. These findings hold important implications for the CLIMAT interview domains, and in general, for the assessment of AD symptoms and treatment response.