Measurement of late-life disability is of interest to policy makers and researchers alike. Valid and reliable measures are necessary to track programmatic eligibility for public health insurance programs such as Medicare and Medicaid and income security programs such as Social Security and Supplemental Security Income. Disability measures are also crucial to accurately projecting the demand for long-term care, to produce actuarial estimates for long-term care insurance, and to understand who is afforded protection under the American with Disabilities Act. Such measures also allow researchers to evaluate the quality of life of older individuals, to understand the causes and consequences of disability in late-life, and to understand the broader public health and policy implications of population aging.
Current measures of late-life disability vary across national surveys. At the same time, most surveys include some version of activities of daily living (ADLs) (Katz 1965, 1970), instrumental activities of daily living (IADLs) (Lawton and Brody 1969), and functional limitations (Nagi 1965, 1991). These measures were initially developed for various clinical purposes during the 1960s and 1970s, and became widely adopted as self-reported items in national surveys during the 1980s and 1990s. Surveys that have maintained identical question wording from year to year have been able to provide two decades worth of evidence on trends in the prevalence of late-life disability (Manton and Gu 2001; Schoeni et al. in press). In addition, panel surveys have provided important insights into disability trajectories, including recovery and decline, and hierarchical patterns (Crimmins and Saito 1993; Dunlop et al. 1997; Mor et al. 1994).
Recent advances in conceptual thinking and measurement of disability provide new opportunities for national surveys to expand upon the array of scientific and policy questions that may be answered with survey data. For example, the addition of vignettes could facilitate comparisons of disability measures across groups and countries with different conceptual understandings of disability (Kapteyn et al. 2004). Moreover, the addition of measures of physical functioning (including performance measures), of assistive technology and the environment, and in time use and participation by older adults would allow analysts to more fully understand the reasons for population-level changes in disability prevalence. Currently, it remains unclear, for example, to what extent changes in disability that occurred during the 1990s reflect changes in underlying functioning, changes in the physical environment of older adults, or shifts in the use of assistive technology (Freedman et al. 2003). Similarly, it remains unclear if declines in IADLs reflect changes in underlying functioning, the physical environment, or changes in the nature of the tasks as a result of technological conveniences (Spillman 2004). Improved measures of the components of disability would also further understanding at the individual level of the physiology of functional loss and recovery (Guralnik et al. 1989), the accommodation process (including use of assistive technologies, personal care and behavioral changes; see Agree 1999), and interventions to enhance independence and participation (Freedman et al. 2005).
Although measurement of work disability has recently been explored by a Committee of the Institute of Medicine (Mathiowetz and Wunderlich 2003), recent advances in the measurement of late-life disability have not been systematically reviewed. To address this gap, the Office of the Assistant Secretary for Planning and Evaluation of the Department of Health and Human Services (HHS) convened a workshop in May 2005 to bring together disability measurement and policy experts to re-think measurement issues around late-life disability in light of national survey efforts. Specifically, the meeting will seek to address two questions:
- Are our current measures of late-life disability meeting the needs of researchers and policy makers?
- How can we improve measures of late-life disability within our current surveys?
This issue brief provides background information on issues that will be raised at the workshop. We include a brief review of disability measurement issues and offer a framework for thinking about disability measurement that will shape the workshop panels and presentations.