Improving the Measurement of Late-Life Disability in Population Surveys Beyond ADLs and IADLs: Summary of a Workshop (2009) / Chapter Skim
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3 Potential Methods for Revising Measures to Foster Comparability Across Subgroups
3 Potential Methods for Revising Measures to Foster Comparability Across Subgroups
Pages 31-50
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From page 31... ...
3. The possible use of easily collected biomarkers of chronic diseases to supplement ADLs and IADLs, which may be able to track de cline in functionality over the life course and capture change in functionality across thresholds 4.
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From page 32... ...
However, performance measures, such as gait speed, chair rises, and pegboard tests, have been used mostly in the domain of functional limitations. Guralnik offered three performance assessments to illustrate the points made in his presentation: gait speed, the index of mobility-related physical limitations (MOBLI)
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From page 33... ...
in which the study population was stratified in two ways -- according to self-reports of being independent in mobility and ADLs and according to categories of SPPB -- and mortality was studied as an outcome. In the group reporting no disability, there was a clear grading of mortality risk across SPPB scores.
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From page 34... ...
The cut points, previously shown to be related to high risk of future adverse events, show a clear age effect, with much higher proportions of people in the 80 years and older group being in the high-risk group according to the SPPB and gait speed, as well as a difference between men and women, with women having poorer functioning. The presentation by Guralnik compared data for SPPB scores of less than or equal to 8 in EPESE, ELSA, and the InCHIANTI study, with substantially poorer performance seen in EPESE.
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From page 35... ...
Trends over time can be directly observed with performance testing, but this will require strict standardization of test administration and quality control procedures to ensure that the tests are administered precisely the same way in every survey. Performance tests can be used to identify high levels of functioning, which cannot be done well with self-reported disability.
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Classical test theory and IRT are different in several ways. Commonly used reliability and validity estimates are based on classical test theory, in which scores on measures are usually obtained by manipulating the item scores (e.g., summing to get a total score)
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With IRT, different people can answer different items yet their scores are estimated on the same mathematical metric. Information function in IRT is analogous to reliability in classical test theory.
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From page 38... ...
One might want to target lower levels of the outcome if that is the population of interest, or one might choose items from the bank that seem particularly relevant for a given clinical population. The important thing to know about item banks is that whether one administers the items with CAT, a long, static instrument, or one of several short forms, the scores are reported on the same mathematical metric.
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From page 39... ...
Defined as such, it does not lend itself to either IRT or classical test theory methods. Functional limitations typically are defined in much narrower terms and are better suited to measurement models.
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From page 40... ...
USE OF EASILY COLLECTED BIOMARKERS OF CHRONIC DISEASES David Weir's (University of Michigan) presentation focused on the possible use of easily collected biomarkers of chronic diseases, to supplement ADL and IADL measures, which may track decline in functionality over the life course and capture changes in functionality across thresholds.
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From page 41... ...
Just counting the number of these difficulties provides some insight into the people who are at risk for developing further disability. Chronic Disease and Disability Weir used a combined measure that is a sum of the Nagi items plus ADL limitations plus IADL limitations discussing chronic disease and disability.
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From page 42... ...
One needs to consider multiple measurement perspectives on obesity. There may be direct effects on mobility: For example, it is harder to move around a lot of weight than a little weight.
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From page 43... ...
And because blood assays are predictors of cardiovascular disease progression, they are expected to predict future cardiovascular events, which then are precipitators of disability. DEVELOPING MEASURES OF TIME USE TO STUDY DISABILITY Vicki Freedman (University of Medicine and Dentistry of New Jersey)
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From page 44... ...
. In the ICF model, health conditions may or may not lead to impairments in body functions and structures that may in turn lead to activity limitations and participation restrictions.
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From page 45... ...
The relative cognitive demands on the respondents vary with each approach. Questions about activities obtained through experiential sampling methods, for example, likely impose the least demand on cognitive skills because of the focus on an immediate time frame.
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Freedman noted that there are well-established techniques for analyzing length-biased samples, but it is not clear that they have been applied to study disability and time use. Disability and Use of Time Development Phase The purpose of the DUST project is twofold: to study the relationship among functioning, time use, and well-being among older couples and to lay the groundwork for potentially collecting time diaries with all adults in the PSID.
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From page 47... ...
The DUST team has spent almost 2 years developing the instrument. The development phase included a series of focus groups, cognitive testing of the instrument, an assessment of the reliability of diary pre-codes, and a pretest with 27 couples.
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From page 48... ...
Rather than asking how much time respondents spent in the last week or month doing specific kinds of activities, DUST included in its cognitive testing and pretest questions of the form: "On how many of the last 7 days did you ____? " Respondents were provided with the following categorical answers to choose from: none, 1–2, 3–4, 5 or more.
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From page 49... ...
Researchers studying trends in disability worry that a screening question might prevent getting information about the prevalence of something asked about in a follow-up question. Fortunately, the items that are presented with a CAT are not screened; they do not keep someone from being asked about some other condition; they only help decide which questions will give the most information about someone's level of, for example, mobility.
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From page 50... ...
Still another issue raised concerns how to interpret the responses if one asks people on how many of the past 7 days they have done some activity that is considered elective. They may choose to do it or not do it.
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