Measuring Physical Capacity: An Assessment of a Composite Measure Using Self-Report and Performance-Based Items

Judith D. Kasper, Kitty S. Chan, Vicki A. Freedman

Research output: Contribution to journalArticle

Abstract

Objective: The objective of this study was to develop and assess a composite measure of physical capacity using self-report and physical performance items. Method: Item response theory (IRT) is used to evaluate measurement properties of self-report and performance items and to develop a composite measure for 7,609 participants in the National Health and Aging Trends Study. Results: Self-reports distinguish differences at the lower end of physical capacity but not at mid-to-high levels. Performance-based measures discriminate across a fuller spectrum. An IRT-based composite score, drawing on both, provides increased measurement precision across the physical capacity spectrum and detects age group differences if either self-report or performance does so - suggesting it is better suited for studying age-related changes than either measure alone. Discussion: Self-report and performance measures have different strengths on the physical capacity spectrum. IRT provides a means of combining these different measurement approaches for analyses of physical capacity across a broad range of functioning in later life.

Original languageEnglish (US)
Pages (from-to)289-309
Number of pages21
JournalJournal of Aging and Health
Volume29
Issue number2
DOIs
StatePublished - 2017

Keywords

  • measurement
  • performance tests
  • physical capacity
  • physical function
  • self-reported function

ASJC Scopus subject areas

  • Health(social science)
  • Sociology and Political Science
  • Life-span and Life-course Studies

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