Psychometric properties of the Dependence Scale in large randomized clinical trials of patients with mild and moderate Alzheimer's disease

Dependence Clusters in Alzheimer Disease and Medicare Expenditures: A Longitudinal Analysis From the Predictors Study

INTRODUCTION

Dependence in Alzheimer disease has been proposed as a holistic, transparent, and meaningful representation of disease severity. Modeling clusters in dependence trajectories can help understand changes in disease course and care cost over time.

METHODS

Sample consisted of 199 initially community-living patients with probable Alzheimer disease recruited from 3 academic medical centers in the United States followed for up to 10 years and had ≥2 Dependence Scale recorded. Nonparametric K-means cluster analysis for longitudinal data (KmL) was used to identify dependence clusters. Medicare expenditures data (1999-2010) were compared between clusters.

RESULTS

KmL identified 2 distinct Dependence Scale clusters: (A) high initial dependence, faster decline, and (B) low initial dependence, slower decline. Adjusting for patient characteristics, 6-month Medicare expenditures increased over time with widening between-cluster differences.

DISCUSSION

Dependence captures dementia care costs over time. Better characterization of dependence clusters has significant implications for understanding disease progression, trial design and care planning.

Utility of the Dependence Scale in dementia: validity, meaningfulness, and health economic considerations

BACKGROUND

The concept of dependence has been proposed as a unified representation of disease severity to quantify and stage disease progression in a manner more informative to patients, caregivers, and healthcare providers.

METHODS

This paper provides a review of the Dependence Scale (DS) as a quantitative measure of Alzheimer's disease severity, its properties as an outcome measure, a metric of disease progression, and a correlate of medical costs.

RESULTS

The literature supports the notion that the DS is related to, but distinct from, key severity measures, including cognition, function, and behavior, and captures the full spectrum of patient needs. It also presents as a useful measure for assessing disease progression.

CONCLUSIONS

Results underscore the importance of the DS as a unique endpoint in Alzheimer's disease clinical trials, providing important information about the impact of therapeutic interventions. The DS also is a useful measure for economic evaluation of novel interventions aimed at delaying progression.

Dependence Stage and Pharmacoeconomic Outcomes in Patients With Alzheimer Disease

The level of assistance patients with Alzheimer disease (AD) require in their care may be an important predictor of resource use, costs of care, and quality of life. The Dependence Scale (DS), a measure of care-assistance required, was used to estimate costs of care and quality of life of patients with AD categorized into 6 dependence stages based upon the summated item scores of the DS. Data were derived from a 3-year, noninterventional study of 132 patients with probable AD (ages, 50 to 85 y) and caregiver dyads. We investigated the association between DS scores and health care costs, health-related quality of life (HRQoL), caregiver burden and estimated annual costs and HRQoL for 6 dependence stages in adjusted models. DS scores were significant predictors of health care costs, HRQoL, and caregiver burden. The estimated annual health care costs and a measure of HRQoL (EuroQoL-5D) ranged from $11,418 and 1.00 for those at very mild dependence stage to $101,715 and 0.26 for those at very severe dependence stage. DS scores classified into 6 dependence stages provides a useful method to estimate unique levels of care-associated costs and health utilities for pharmacoeconomic evaluations of new treatments for AD.

A Path Analysis of Dependence and Quality of Life in Alzheimer's Disease

OBJECTIVE

To determine the direct and indirect relationships of cognitive, functional, and behavioral factors and other medical comorbidities with the quality of life (QoL) of patients with Alzheimer's disease (AD) according to the theoretical model of dependence.

METHODS

Observational and cross-sectional study. Cognitive and functional status, behavior, dependence, medical comorbidities, and QoL were assessed by using standardized instruments. A path analysis was used to model the direct and indirect relationships among clinical indicators according to the theoretically based model of dependence.

RESULTS

The sample consisted of 343 patients with AD (32.1% mild, 36.7% moderate, and 31.2% severe). Medical comorbidities, disease severity, and dependence level had a direct relationship with QoL. The functional disability and the behavior disturbances were indirectly related to QoL via dependence level, and the cognitive impairment was indirectly related to QoL via severity level.

CONCLUSION

Direct and indirect effects exist between clinical indicators, dependence, and QoL.