Sociodemographic and clinical correlates of utility scores in Alzheimer's disease

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.

Health state values for use in the economic evaluation of treatments for Alzheimer's disease

Alzheimer's disease (AD) is a chronic, progressive, neurodegenerative disease that places a heavy burden on people with the condition, their families and carers, health care systems and society in general. Health-related quality of life (HR-QOL) in patients deteriorates as the cognitive, behavioural and functional symptoms of AD develop. The human and financial cost of AD is forecast to grow rapidly as populations age, and those responsible for planning and financing health care face the challenge of allocating increasingly scarce resources against current and future interventions targeted towards AD. These include calls for early detection and diagnosis, preventative strategies, new medications, residential care, supportive care, and meeting the needs of carers as well as patients. Health care funders in many health systems now require a demonstration of the value of new interventions through a comparison of benefits in terms of improvements in HR-QOL and costs relative to those of competing or existing practices. Changes in HR-QOL provide the basis for the calculation of the quality-adjusted life-year (QALY), a key outcome used in economic evaluations to compare treatments within and between different disease conditions. The objective of this systematic review was to provide a summary of the published health state values (utilities) for AD patients and their carers that are currently available to estimate QALYs for use in health economic evaluations of interventions in AD. The health care literature was searched for articles published in English between 2000 and 2011, using keywords and variants including 'quality-adjusted life years', 'health state indicators', 'health utilities' and the specific names of generic measures of HR-QOL and health state valuation techniques. Databases searched included MEDLINE, EMBASE, NHS EED, PsycINFO and ISI Web of Science. This review identified 12 studies that reported utility values associated with health states in AD. Values for AD health states categorized according to cognitive impairment (where 1 = perfect health and 0 = dead) ranged from mild AD (0.52-0.73) to moderate AD (0.30-0.53) to severe AD (0.12-0.49). Utility values were almost all based on two generic measures of HR-QOL: the EQ-5D and Health Utility Index mark 2/3 (HUI2/3). There were no health state values estimated from condition- or disease-specific measures of HR-QOL. The review also identified 18 published cost-utility analyses (CUAs) of treatments for AD. The CUAs incorporated results from only three of the identified health state valuation studies. Twelve CUAs relied on the same study for health state values. We conclude that the literature on health state values in AD is limited and overly reliant on a single symptom (cognition) to describe disease progression. Other approaches to characterizing disease progression in AD based on multiple outcomes or dependency may be better predictors of costs and utilities in economic evaluations. Patient and proxy ratings were poorly correlated, particularly in patients with more advanced AD. However, proxy ratings displayed the validity and reliability across the entire range of AD severity needed to detect long-term changes relevant to economic evaluation. Further longitudinal research of patient and carer HR-QOL based on multidimensional measures of outcome and utilities is needed.

Caregiver burden, health utilities, and institutional service use in Alzheimer's disease

OBJECTIVE

This study examined the moderating effect of caregiver burden on the relationship between the health status of Alzheimer's disease (AD) patients and their use of institutional services (i.e., hospitalization, nursing home, and residential care).

METHODS

Data were obtained at baseline and at 3, 6, and 9 months following study entry on 421 community-dwelling patients with AD in the Clinical Antipsychotic Trials of Intervention Effectiveness for AD. The outcome variable includes use of any institutional services. Logistic regression was employed to estimate the interaction between Health Utility Index Mark III score (a general health status measure) and four concurrent caregiver burden measures at outcome. Marginal effects were calculated and plotted using random effects models for observations at multiple time points per individual. Average effects were calculated across all observations using models without random effects.

RESULTS

Random effects results suggest that caregiver burden weakens the inverse relationship between health utilities and institutional service use, leading to greater likelihood of institutional use than would be expected at a given level of health. This is indicated by positive and significant signs on the Health Utility Index Mark III*caregiver burden interaction when burden is measured using the Caregiver Distress Scale, Beck Depression Inventory, and Caregiver Assessment Survey (all p < 0.05). It is reinforced by positive and significant average effects deriving from Caregiver Distress and Beck Depression Inventory models without random effects (both p < 0.10). Results derived from the Burden Interview Scale, although positive, were non-significant and weak by comparison.

CONCLUSION

Caregiver support interventions should be offered to individuals caring for less-advanced AD patients. Otherwise, healthy patients may be at increased risk for institutionalization when caregivers experience high levels of burden.

Gender differences in quality of life among Canadian adults with epilepsy

The clinical literature suggests epilepsy may impact quality of life in males and females differently. Previous research on gender issues has focused primarily on biological-biomedical factors over psychological and social factors. In this study we compare subjective and objective quality of life in adult persons with epilepsy to persons without epilepsy by gender using the biopsychosocial model in the Canadian Community Health Survey (CCHS), a large epidemiological survey that covers 98% of the Canadian population. Logistic regression analyses were conducted using self-rated health status and the Health Utility Index(®) 3 (HUI3) as the outcomes. Quality of life was significantly moderated after controlling for the biological-biomedical variables in all analyses except the HUI3. Males with epilepsy were more likely to have HUI3 scores of 0.70 or greater than males without epilepsy (OR = 1.61, 95%CI 1.32-1.96). For males with epilepsy the HUI3 was further moderated, but remained significantly better in the final model that controlled for biological, psychological and social factors (OR = 1.43, 95%CI 1.17-1.76). Our findings provide support for treatment approaches that focus on the whole person. Such approaches should take into account gender differences when examining objective quality of life.

Caregiver burden, health utilities, and institutional service costs among community-dwelling patients with Alzheimer disease

This study examined the moderating effect of caregiver burden on the relationship between patients' health status and institutional costs in Alzheimer disease (AD). Data were obtained on whether 421 community-dwelling patients with AD in the CATIE-AD trial received institutional services in the month preceding baseline and at 3-month, 6-month, and 9-month follow-up. All participants had a caregiver who lived with or visited them regularly. Outcome variables include hospital, nursing home, residential, and combined institutional costs. Mixed models were employed to estimate the interaction of Health Utility Index (HUI)-III scores (a health status measure) and 5 measures of caregiver burden. Wherever significant, results indicate that greater caregiver burden weakens the inverse relationship between health utilities and institutional costs, leading to greater costs than would be expected at a given level of health. Altogether 45.0% of the models (9/20) showed this effect (positive coefficient on the burden-HUI interaction term). Interventions to support caregivers should be based on caregiver burden, regardless of care recipient health status, for even seemingly manageable patients may be at heightened risk for institutionalization if caregivers experience sufficiently high levels of burden.

Assessing the relationship between health utilities, quality of life, and health services use in Alzheimer's disease

OBJECTIVES

To examine the relationship between use of multiple health services and health utilities, quality of life and other factors in Alzheimer's disease (AD).

DESIGN

Data were obtained via caregiver proxy at baseline and 3- 6- and 9-months post-random assignment among 421 community-dwelling AD patients participating in the CATIE-AD trial of anti-psychotic medications. Service use includes both institutional and outpatient services. Correlates include the AD-Related Quality of Life Scale (ADRQoL), Health Utilities Index (HUI)-III, Neuropsychiatric Inventory, Mini Mental Status Examination, and AD-Cooperative Study Activities of Daily Living Scale. Chi squared tests, t-tests and logistic regression (using general estimating equations) were used to examine the correlates of service use.

RESULTS

Three quarters (74.2%) used at least one service each month. Average monthly utilization rates for specific service types were: 4.5%, inpatient hospital; 5.6%, nursing home; 3.9%, residential care; 44.0%, AD-related outpatient; 9.4%, mental health outpatient; and 45.5%, medical-surgical outpatient. The likelihood of using any service was higher among older patients [Odds Ratio (OR) = 1.03] and non-Hispanic Whites (OR = 1.61). Each 0.10 increment on the Health Utilities Index (HUI)-III was associated with a 7.0% decrease in the odds of using one or more service (OR = 0.93). The odds of using outpatient and institutional services were 6.0% and 10.0% lower, respectively, for each 0.10 increment on the HUI-III (OR = 0.94, OR = 0.90). The AD-Related Quality of Life Scale proved significantly related to outpatient medical-surgical services only (OR = 1.01).

CONCLUSION

Findings suggest that the HUI-III could be combined with other known correlates of service use to inform population planning associated with AD.