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Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Executive Deputy EditorIndividualAuthor
To the Editor: Dr Liao and colleagues1 addressed the important issue of compression of
morbidity by analyzing data from the 1986 and 1993 National Center for Health
Statistics National Mortality Followback Surveys, and found an overall improvement
in quality in the last year of life among persons aged 85 years and older.
Unfortunately, this work is flawed because of major methodological differences
in the 2 surveys. First, the questions used to estimate prevalence of impairments
in activities of daily living (ADLs) are strikingly different in the 2 surveys.
Questions in 1986 asked about help or use of special equipment to perform
ADLs, whereas those in 1993 asked whether the decedent had any difficulty
performing these tasks. These are very different concepts and may provoke
different responses, thus introducing bias into the results. For example,
persons using special equipment to walk or bathe may not be perceived as having
difficulty. A recent study shows that individuals respond very differently
to these 2 types of questions.2
The 1986 survey was primarily a mail survey; the 1993 survey was primarily
a telephone survey with no mail interviews. Different modes of data collection
may produce different results, but the authors did not identify these differences
or evaluate this impact. Moreover, the 2 series of questions used to assess
overnight stays in hospitals and nursing homes were quite different.
Unfortunately, Liao et al suggest that methods on the 2 surveys were
identical and state that "considerable effort was made to maintain comparability
of the 2 surveys, including design and data collection." They should provide
readers with the information necessary to understand how these differences
might have affected their results.
Lentzner HR. Quality of Life at the End of Life. JAMA. 2000;284(12):1513–1515. doi:10.1001/jama.284.12.1512
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