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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2 Challenges to Improving Measurement of Late-Life Functioning and Disability
2 Challenges to Improving Measurement of Late-Life Functioning and Disability
Pages 11-30
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From page 11... ...
Self-responses versus proxy responses in surveys 4. Expanding modes of survey administration POPULATION SURVEY MEASURES OF FUNCTIONING: STRENGTHS AND WEAKNESSES Barbara Altman (disability statistics consultant)
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While each of these succeeding models has made contributions, the original model is still very visible. On the basis of these models, major conceptual elements that make up the experience of disability and need to be measured in population surveys include (the background paper and this discussion focus only on those concepts that are starred)
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measurement in a population survey involves decision points, and with each decision point the initial basic concept is narrowed. Because of the limitations associated with population surveys -- time, space, and cost -- it is hard to include all the conceptual elements identified in a full theoretical model of disability.
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The second purpose of collecting data in a population survey is to demonstrate the provision of service and programmatic needs of a population. Measures of service needs are generally focused on particular types of impairment, functional limitation, or age groupings and usually involve such subpopulations as wheelchair users, people who have problems communicating, or people with spinal cord injuries.
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However, the current models of disability reflect a hierarchy or an increasing complexity of the components associated with the disability process. In addition to the representation of the presence of an impairment or an impairing condition, there are at least four levels of measurement reflected in disability conceptual models: basic action, specific task, organized activity, and role participation.
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Finally, participation represents the accomplishment of enough organized activities to satisfy minimum role requirements to be considered integrated in a specific role. Measures in Population Surveys Almost all population surveys with disability measures include impairment measures.
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began her presentation with a question: How can one identify people early in the disablement process? In other words, is there life before ADL and IADL limitations -- looking at disease, predicting impairments, predicting functional limitations, predicting disability?
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Self-reported task difficulty in more demanding tasks can, itself, identify people early in a disablement process and possibly presage incipient disease. For example, unpublished data from the Cardiovascular Health Study (Fried et al., 1991a)
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They also found that preclinical status in terms of mobility in these middle-aged African Americans living in the inner city predicted a fourand-a-half-fold increased risk of onset of difficulty in walking a half mile, with preclinical disability again defined as self-report of modifications in the way people went about doing mobility tasks but without difficulty.
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Basically, people report doing the task more slowly, changing their body position, or doing the activity less frequently; then they cut out parts of the activity that they would normally do in a day; and then they start using assistive devices and human assistance. This work offers one perspective on using surveys to identify people with earlier changes in function in a way that can be used for targeting for prevention of disability.
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From page 21... ...
In addition to asking about disability at the present time, for each of the four essential ADLs, participants who did not need help from another person "at the present time" were asked to recall whether they needed help from another person to complete the relevant task "at any time" during the past 1 month, 3 months, 6 months, and 12 months, respectively. Focusing on the 12-month results, up to one-half of the incident disability episodes, which would otherwise have been missed by asking only about disability at the present time, could have been ascertained if nondisabled persons had also been asked to recall whether they had had a disability at any time since the prior assessment.
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From page 22... ...
presentation dealt with the use of proxies to obtain information on health and functioning of older persons in population surveys, describing some of the issues, suggesting some practical strategies for using data from proxies, and identifying areas for additional study. He noted that there have not been any major breakthroughs in the use of proxies in the past several years, and so a lot of the information comes from work that was done some time ago.
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There may be other areas, but these are some that have been examined. The major issues related to subject and proxy agreement are no different from the kinds of issues faced in any kind of scientific measurement.
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. Similar analysis was done with data on a post-hip fracture group; for which proxies overreported depressive symptoms but clealy underreported cognitive problems; that is, proxies said that the person actually performed better than was shown in a test of cognition.
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Evaluate the effects of substituting proxy data on parameter estimates; evaluate the effect of using only proxies, especially when bias is significant, and evaluate the effects of using information from multiple sources in the same analysis to arrive at assessment of functional status. In conclusion, proxies can be used with a reasonable degree of reliability for some questions.
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From page 26... ...
In countries with low Internet penetration, using the Internet as the only survey mode would lead to coverage error. Yet other modes, such as the telephone, also have problems; telephone interviews that use only land lines increasingly suffer from the same problem of coverage, and there are also problems because of answering machines that screen calls.
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From page 27... ...
Other issues of note were use of the Internet for data collection, the role of the home environment for conducting performance tests, and phobias in old age. Use of Internet for Data Collection A participant noted an interesting aspect of using the Internet for data collection, as well as any of the research looking at age differences and use of the Internet, namely, that there actually are age differences in sensory perception and ability to physically use a computer interface.
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From page 28... ...
For very old respondents, the first thing needed is that the letters have to be big, and the screen should not be cluttered -- it has to be as simple as possible, otherwise people get confused. Role of the Home Environment for Conducting Performance Tests Linda Fried was asked if in her studies she and her colleagues had studied the differences that the home environment makes in conducting performance tests with different populations.
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From page 29... ...
In addition to the discussion of a gold standard for proxy measurement, other issues about proxies drew lively discussion. Participants reiterated several points made in the presentation: One of the reasons for bias in responses in proxy measurement might be characteristics of the proxy, such as gender.
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From page 30... ...
The choice may be dependent on the question to be asked, and who has the best opportunity to observe the subject? For example, in a nursing home, perhaps the family proxy is not the best person but someone who sees the subject all the time on a daily basis.
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