COGNITIVE AND PHYSICAL BASIS OF DISABLEMENT

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This research will test a causal model of "disablement,"in which impairment (low scores on tests of motor or cognitive performance) and functional limitation (inefficient or unsafe performance of daily tasks) result in disability (recognition of difficulty or need for help in instrumental and basic activities of daily living [IADL/BADL]). We will follow 360 elders recruited from an existing multi-ethnic community-based study, the Washington Heights-Inwood Columbia Aging Project (WHICAP), all of whom will have mild-to-moderate disability and not meet criteria for dementia. They will be assessed 3 times, 18 months apart. Within disability groups (1, 2, or 3 domains based on self-reports), half of the subjects will be cognitively normal and half will have mild cognitive impairment or questionable dementia. We will assess the direct and indirect effects of impairment and functional limitation on disability in groups defined by self-reported disability status and cognitive performance, in different race-ethnic groups (African-American, Hispanic, white), and longitudinally. In addition, we will assess the accuracy of self- and proxy-reports of disability using a clinical diagnosis (established in a clinical consensus conference) as a gold standard, and alternatively through use of latent class models that do not assume a gold standard. An important feature of this research is its use of the assessment of Motor and Process Skills (AMPS) , an occupational assessment tool for rating functional limitation in the activities of daily living. AMPS evaluations yield scores for motor and cognitive/process limitations that interfere with efficient and safe performance of IADL/BADL tasks. OT's will conduct AMPS evaluations in subject homes, along with detailed assessments of physical impairment (as well as measures of home and neighborhood environment). The parent WHICAP study will provide data on cognitive performance and neurologic-medical status. Our major goal is to test a causal (structural equations) model of disablement. We hypothesize that impairment is related to disability directly but also indirectly through observed motor and cognitive/process limitations. We will test whether this indirect effect is stronger for some groups of elders (e.g., mild disabled) than others. This finding would suggest that disability may be reduced through remediation of motor and cognitive/process skills, as well as by efforts to reduce impairment.