Self-report of functional abilities in older adults with mental retardation: ADLs and IADLs. (Activities of Daily Living, Instrumental Activities of Daily Living)

The purpose of this study was to examine the validity and reliability of self-report in determining functional abilities in older adults with mental retardation. Thirty participants were interviewed twice using the index of Activities of Daily Living (ADL) and the Instrumental Activities of Daily Living (IADL) scale, which were modified to include structured probes. The participants' self-reports were compared to informant report from their care providers. Significant test-retest reliability and a significant correlation between participants' self-reports and informant reports were found. Reliability and validity of the index of ADL were increased by eliminating the item on incontinence. Analysis of the data confirmed the hypothesis that the modified ADL and IADL instruments could be used to obtain reliable and valid self-report data regarding functional ability in older adults with mental retardation. This information is useful to professionals in the generic aging service system who are now serving persons with mental retardation.

Aging persons with mental retardation have rarely been the subjects of research in the past, primarily due to their reduced life expectancy and a hidden existence in institutions and hospitals. Changing demographics, improved health care, and an emphasis on community dwelling have brought the first cohort of older persons with mental retardation into the public arena as service consumers. Providers of generic aging services are currently challenged by the need to integrate older persons with mental retardation into existing community-based programs. Gathering information from consumers regarding their abilities and needs is an ongoing process in service provision. Questions have been raised, however, regarding the best way to elicit information from persons with mental retardation. Intellectual and adaptive limitations may restrict the ability of persons with mental retardation to communicate their competencies and needs effectively (Straw & Budd, 1983; Sigelman et al., 1980). The best question format to use with persons with mental retardation of higher IQ to promote comprehension and response is still unclear.

As in the typical older adult population, the measurement of functional abilities is vital to determining the needs and priorities of older persons with mental retardation. As reflected in the new functionally based definition of mental retardation published by the American Association on Mental Retardation (AAMR), measurement of one's limitations in adaptive skills is an integral part of identifying what supports are needed by an individual with mental retardation (AAMR, 1992). Additionally, the assessment of functional abilities in areas such as activities of daily living (ADL) is used to establish eligibility for a wide range of services in both the aging and developmental disabilities service networks (AAMR, 1992; Kane, Saslow, & Brundage, 1991). Because rescreening must be done periodically to establish continued eligibility and to identify changing service needs, self-report instruments are commonly used in generic aging services. The use of self-report with this subpopulation of older adults with mental retardation, however, has not been thoroughly examined.

The evidence regarding the accuracy of self-report measures of physical functioning is mixed, depending in part on whether self-report is compared to direct observation or to informant report. Although many studies examining the accuracy of self-report in the measurement of functional abilities have found that self-report has limited validity and is adversely affected by cognitive impairments and other factors (Edwards, 1990; Kivela, 1984; Kuriansky, Gurland, & Fleiss, 1976; Rubenstein, Schairer, Weiland, & Kane, 1984), these studies typically used different measures for self-report, informant report, and direct observation. The use of different scales for different informants introduces the possibility that each scale measures different aspects of functional ability (Little, Hemsley, Volans, & Bergmann, 1986). Using identical items for self-report and informant report, Dorevitch et al. (1992) found that older adults in the general population are more accurate sources of information about their own functional abilities than are knowledgeable caregivers, who tend to underestimate the individual's abilities. Direct observation is usually considered the most valid method for measuring functional ability; however, in many situations, observation of the target behavior is simply not feasible, and the practitioner must depend on either self-report or informant report.

There is evidence that adults with mental retardation who have sufficient communicative skills to answer questions are sources of valid information not only about internal psychological or emotional states (Kazdin, Matson, & Senatore, 1983; Reynolds & Baker, 1988; Senatore, Matson, & Kazdin, 1985) but also about their adaptive behavior skills (Voelker et al., 1990, Unfortunately, there are no well-established instruments designed for the measurement of functional-adaptive abilities by self-report for older adults with mental retardation. The Vineland Adaptive Behavior Scales (VABS) have been used with self-report …