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Authors' Response

Beth Israel Deaconess Medical Center Harvard Medical School Boston, Massachusetts
Schools of Medicine and Public Health Johns Hopkins University Baltimore, Maryland
Laboratory of Epidemiology, Demography, and Biometry National Institute on Aging Bethesda, Maryland

Address correspondence to Suzanne Leveille, 330 Brookline Ave., RD-103, Boston, MA 02215. E-mail: sleveill{at}bidmc.harvard.edu

To the Editor:

We appreciate the difficulties of identifying the symptom causes of disability in moderately to severely cognitively impaired older adults. As Di Fazio and colleagues state in their letter, this represents a large segment of the older population that was not included in our initial paper proposing a symptom and impairment-based classification of disability (1). Further validation of our proposed taxonomy is needed in diverse populations of elders, inclusive of the full spectrum of symptoms and impairments that may directly impact daily self-care activities. However, we do not believe that currently available objective measures of functioning will necessarily provide the gold standard of proof regarding the main causes of disability that we have categorized in our taxonomy. Our analyses examining physical performance showed that, although the results were in the direction we would have expected, for example, women with balance-related disability performed poorly in standing balance tests, there were many other women with poor balance performance that did not attribute their disability to a balance problem (2). This latter issue is consistent with the multifactorial nature of disability.

Objective measures of functioning provide information often proximal to the end-point of disability, but these measures will not confirm or refute the significant contribution of symptoms such as pain and general weakness or fatigue that so many older women in our study reported as main causes of their disability. Our classification does not ignore the large body of evidence showing that disability is often the end result of multiple limitations, but we know that many elders live for years with chronic functional limitations and remain independent. Our findings shed light on the symptom–disability relationships that have not been adequately addressed in the etiological research examining causes of disability. In the data presented by Di Fazio and colleagues, it would be helpful to know whether and to what degree aspects of cognitive impairment influenced difficulty with mobility or activities of daily living.

Received June 3, 2004

Accepted June 3, 2004

References

3. Di Fazio I, Franzoni S, Trabucchi M. Advancing in the analysis of disability in cognitively impaired older adults. J Gerontol Med Sci 2004;59A:1077.
4. Leveille SG, Fried LP, McMullen W, Guralnik JM. Advancing the taxonomy of disability in older adults. J Gerontol Med Sci. 2004;59A:86-93.

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