Measurement equivalence in ADL and IADL difficulty across international surveys of aging: Findings from the HRS, SHARE, and ELSA

Kitty S. Chan, Judith D. Kasper, Jason Brandt, Liliana E. Pezzin

Research output: Contribution to journalArticle


Objective.To examine the measurement equivalence of items on disability across three international surveys of aging.Method.Data for persons aged 65 and older were drawn from the Health and Retirement Survey (HRS, n = 10,905), English Longitudinal Study of Aging (ELSA, n = 5,437), and Survey of Health, Ageing and Retirement in Europe (SHARE, n = 13,408). Differential item functioning (DIF) was assessed using item response theory (IRT) methods for activities of daily living (ADL) and instrumental activities of daily living (IADL) items.Results.HRS and SHARE exhibited measurement equivalence, but 6 of 11 items in ELSA demonstrated meaningful DIF. At the scale level, this item-level DIF affected scores reflecting greater disability. IRT methods also spread out score distributions and shifted scores higher (toward greater disability). Results for mean disability differences by demographic characteristics, using original and DIF-adjusted scores, were the same overall but differed for some subgroup comparisons involving ELSA.Discussion.Testing and adjusting for DIF is one means of minimizing measurement error in cross-national survey comparisons. IRT methods were used to evaluate potential measurement bias in disability comparisons across three international surveys of aging. The analysis also suggested DIF was mitigated for scales including both ADL and IADL and that summary indexes (counts of limitations) likely underestimate mean disability in these international populations.

Original languageEnglish (US)
Pages (from-to)121-132
Number of pages12
JournalJournals of Gerontology - Series B Psychological Sciences and Social Sciences
Volume67 B
Issue number1
StatePublished - Jan 2012


  • Activities of daily living
  • Differential item functioning
  • Disability

ASJC Scopus subject areas

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

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