Validation of the Late-Life Function and Disability Instrument

Authors

  • Stephen P. Sayers PhD,

    1. From the *Human Physiology Laboratory, Department of Health Sciences, Roybal Center for the Enhancement of Late Life Function, Sargent College of Health and Rehabilitation Sciences, School of Public Health, Department of Epidemiology/Biostatistics, Boston University, Boston, Massachusetts§Epidemiology, Demography, and Biometry Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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  • Alan M. Jette PT, MPH, PhD,

    1. From the *Human Physiology Laboratory, Department of Health Sciences, Roybal Center for the Enhancement of Late Life Function, Sargent College of Health and Rehabilitation Sciences, School of Public Health, Department of Epidemiology/Biostatistics, Boston University, Boston, Massachusetts§Epidemiology, Demography, and Biometry Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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  • Stephen M. Haley PT, PhD,

    1. From the *Human Physiology Laboratory, Department of Health Sciences, Roybal Center for the Enhancement of Late Life Function, Sargent College of Health and Rehabilitation Sciences, School of Public Health, Department of Epidemiology/Biostatistics, Boston University, Boston, Massachusetts§Epidemiology, Demography, and Biometry Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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  • Tim C. Heeren PhD,

    1. From the *Human Physiology Laboratory, Department of Health Sciences, Roybal Center for the Enhancement of Late Life Function, Sargent College of Health and Rehabilitation Sciences, School of Public Health, Department of Epidemiology/Biostatistics, Boston University, Boston, Massachusetts§Epidemiology, Demography, and Biometry Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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  • Jack M. Guralnik MD, PhD,

    1. From the *Human Physiology Laboratory, Department of Health Sciences, Roybal Center for the Enhancement of Late Life Function, Sargent College of Health and Rehabilitation Sciences, School of Public Health, Department of Epidemiology/Biostatistics, Boston University, Boston, Massachusetts§Epidemiology, Demography, and Biometry Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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  • Roger A. Fielding PhD

    1. From the *Human Physiology Laboratory, Department of Health Sciences, Roybal Center for the Enhancement of Late Life Function, Sargent College of Health and Rehabilitation Sciences, School of Public Health, Department of Epidemiology/Biostatistics, Boston University, Boston, Massachusetts§Epidemiology, Demography, and Biometry Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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  • This study was supported by National Institute on Aging Contracts 263-MA-202876 and R01-AG-18844, Roybal Center for the Enhancement of Late-Life Function Grant P50-A11669, and a National Institute on Disability, Rehabilitation Research Post-Doctoral Fellowship in Health Services Research (H133P99004) to Dr. Sayers.

Address correspondence to Stephen P. Sayers, University of Missouri-Columbia, School of Health Professions, Department of Physical Therapy, 114 Lewis Hall, Columbia, MO 65211. E-mail: sayerss@missouri.edu

Abstract

Objectives: To assess the concurrent and predictive validity of the Late-Life Function and Disability Instrument (LLFDI).

Design: Cross-sectional.

Setting: University-based human physiology laboratory.

Participants: One hundred one men and women aged 80.8±0.4.

Measurements: A short physical performance battery (SPPB) and a self-paced 400-m walk (400-m W) were used as performance tests of lower extremity function. The LLFDI was used to assess self-reported function and physical disability. Partial correlations adjusted for age and body mass index were used to determine the concurrent and predictive validity of the LLFDI. Statistical significance was accepted at P<.004 using a testwise correction.

Results: LLFDI Overall Function scores were moderately associated with the SPPB (r=0.65, P<.001), 400-m W gait speed (r=0.69, P<.001), and measures of lower extremity function. Correlations of the two lower extremity subscores of the LLFDI (correlation coefficient (r)=0.63–0.73, P<.001) were greater than for the LLFDI upper extremity subscores (r=0.19–0.26, P>.004). Performance measures of function predicted disability limitations in the range of r=0.37–0.44 (P<.001) and disability frequency in the range of r=0.16–0.20 (P>.004).

Conclusion: These findings support the concurrent and predictive validity of the LLFDI. Results support the use of the LLFDI scales as a substitute for physical performance tests when self-report is a preferred data-collection format.

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