To examine the relationship between psychiatric symptoms, cognitive performance, functional capacity and quality of life in Alzheimer's disease (AD), and change in the Health Utilities Index (HUI)—Mark III, a widely used generic, multiattribute preference-based health-status classification system.
Follow-up data were obtained from caregiver proxy raters at 3, to 6, and 9-months postrandom assignment concerning 421 patients with AD, living with at least one caregiver in a noninstitutional setting, who participated in the Clinical Antipsychotic Trial of Intervention Effectiveness—AD of antipsychotic medication. Spearman rank correlations, multivariate linear regression, and mixed modeling were used to examine the correlates of change in the HUI.
HUI scores decreased by an average of −0.061 over 9 months. Analysis revealed weak bivariate, and largely, nonsignificant multivariate relationships between change in HUI scores and sociodemographic characteristics, psychiatric symptoms, and cognitive performance. There were highly significant associations between decreases in health utilities and change in the AD Cooperative Study for Activities of Daily Living scale (ADCS-ADL) and AD-Related Quality of Life (ADRQoL) (both P 0.001), even after controlling for other factors. Adjusted R values ranged from 0.14 to 0.20.
In AD patients requiring antipsychotic treatment, only weak relationships were found between changes in the HUI and sociodemographic and clinical indicators. While functional capability and quality of life showed more significant associations, less than 20% of the variance in health utility could be explained. Significant cognitive impairment and the need to rely on proxy raters may limit the usefulness of utility measurement in AD patients with serious behavioral symptoms.