TY - JOUR
T1 - Measurement equivalence in ADL and IADL difficulty across international surveys of aging
T2 - Findings from the HRS, SHARE, and ELSA
AU - Chan, Kitty S.
AU - Kasper, Judith D.
AU - Brandt, Jason
AU - Pezzin, Liliana E.
N1 - Funding Information:
This research was supported by the National Institute on Aging (grant AG032502).
PY - 2012/1
Y1 - 2012/1
N2 - 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.
AB - 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.
KW - Activities of daily living
KW - Differential item functioning
KW - Disability
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U2 - 10.1093/geronb/gbr133
DO - 10.1093/geronb/gbr133
M3 - Article
C2 - 22156662
AN - SCOPUS:84856479369
SN - 1079-5014
VL - 67 B
SP - 121
EP - 132
JO - Journals of Gerontology - Series B Psychological Sciences and Social Sciences
JF - Journals of Gerontology - Series B Psychological Sciences and Social Sciences
IS - 1
ER -