Measurement equivalence in ADL and IADL difficulty across international surveys of aging: findings from the HRS, SHARE, and ELSA. J Gerontol B Psychol Sci Soc Sci 2012 Jan;67(1):121-32
Date
12/14/2011Pubmed ID
22156662Pubmed Central ID
PMC3267026DOI
10.1093/geronb/gbr133Scopus ID
2-s2.0-84856479369 (requires institutional sign-in at Scopus site) 80 CitationsAbstract
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.
Author List
Chan KS, Kasper JD, Brandt J, Pezzin LEAuthor
Liliana Pezzin PhD, JD Professor in the Institute for Health and Equity department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Activities of Daily LivingAged
Aged, 80 and over
Aging
Bias
Europe
Female
Health Surveys
Humans
Internationality
Longitudinal Studies
Male
United States
