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Journal of Geriatric Physical Therapy:
Poster Presentations

DIRECT AND INDIRECT EFFECTS OF COGNITIVE PROCESSING AND PHYSICAL FUNCTION ON DISABILITY IN OLDER ADULTS.

Schrodt, L.1; Giuliani, C.2; Mercer, V.2; Freburger, J.3; Hartman, M.4; Busby‐Whitehead, J.5

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Author Information

1Department of Physical Therapy, Western Carolina University, Cullowhee, NC;

2Center for Human Movement Science, University of North Carolina at Chapel Hill, Chapel Hill, NC;

3Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill, NC;

4Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC;

5Program on Aging, University of North Carolina at Chapel Hill, Chapel Hill, NC.

Purpose/Hypothesis: Age‐associated cognitive decline is associated with an increased risk of falls and poorer performance of mobility and daily living tasks in older adults. Understanding how cognitive processing contributes to everyday task performance is important for designing effective intervention programs for older adults. The purposes of this study were to examine: 1) the direct effect of cognitive processing on disability and the indirect effect mediated by physical function, and 2) if the relationship between physical function and disability is modified by cognitive processing. Subjects: Community dwelling older adult volunteers (N=155) from a continuing care retirement community and church congregation (mean age 81.2 ± 5.7 years, 71% female) who participated in a wellness assessment that included measures of cognitive processing, physical function, and disability. Materials/Methods: Cognitive processing, defined as performance on measures of attention and processing speed, was assessed with the Symbol Digit Modalities Test (SDMT) and the Trail Making Test Part B (TMTB). Raw SDMT and TMTB scores were transformed into z‐scores to create a composite cognitive processing score. Physical function was assessed with the Physical Performance Test (PPT) and walking speed (WS). The SF‐36 Physical Function Sub‐scale (PF‐10) assessed disability. Linear regression models were estimated to examine the direct and indirect relationships among cognitive processing, physical function, and disability. Results: Higher levels of cognitive processing were associated with higher levels of physical function and lower levels of disability (Pearson correlation coefficient range .42 to .60, p <.001). Cognitive processing explained approximately 14% of the variance in PF‐10 (p <.001), primarily though indirect effects mediated by physical function. The indirect effect of cognitive processing on PF‐10, mediated by PPT or WS, was significant (p <.001); however, the direct effect of cognitive processing on PF‐10 was not significant. The magnitude of the indirect effects of cognitive processing on PF‐10 were similar with PPT or WS as the mediator. The relationship of PPT or walking speed to PF‐10 was not modified by level of cognitive processing. Conclusions: The relationship between cognitive processing and disability is primarily mediated by physical function, illustrating the importance of cognitive processing on physical function and its indirect relationship to disability. Through this indirect path, decreased cognitive processing is associated with increased disability. Clinical Relevance: The results of this study support the importance of understanding how the combined effects of cognitive processing and physical function contribute to disability in older adults. Clinicians should consider cognitive processing abilities as they develop comprehensive treatment programs to improve physical function and independence in older adults.

Copyright © 2006 the Section on Geriatrics of the American Physical Therapy Association

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