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To evaluate two psychometric properties of SF-36, namely unidimensionality and reliability.The data are from three cohorts in the HALCyon collaborative research programme into healthy ageing: Aberdeen Birth Cohort 1936 (n = 428), Hertfordshire Ageing Study (n = 358) and Hertfordshire Cohort Study (n = 3,216). The Mokken scaling model was applied to each sub-scale of SF-36 to evaluate unidimensionality as indicated by scalability. The lower bound for internal consistency reliability was determined by Cronbach's alpha.All six sub-scales of SF-36, with the exception of general health (GH) and mental health (MH), demonstrated strong scalability (0.5 ≤ H < 1). The results were consistent across all 3 cohorts. Both GH and MH showed medium scalability (0.4 ≤ H <0.55), although individual items 'sick easier..', 'as healthy as..' and 'expect to get worse' of the GH sub-scale and 'nervous', 'happy' in the MH sub-scale had low scalability (H < 0.4) in the oldest cohort (aged 73-83). Cronbach's alphas for all sub-scales were between 0.70 and 0.92.The unidimensionality and reliability of the sub-scales of SF-36 are sufficient to make this a useful measure of health-related quality of life in older people. Caution is needed when interpreting the results for GH and MH in the oldest cohort due to the poor unidimensionality.

Original publication

DOI

10.1007/s11136-010-9838-7

Type

Journal article

Journal

Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation

Publication Date

09/2011

Volume

20

Pages

1005 - 1010

Addresses

MRC Unit for Lifelong Health and Ageing, University College London, 33, Bedford Place, London, WC1B 5JU, UK. g.mishra@nshd.mrc.ac.uk

Keywords

HALCyon Study Team, Humans, Health Surveys, Cohort Studies, Reproducibility of Results, Psychometrics, Health Status, Quality of Life, Aged, Middle Aged, Scotland, Female, Male, Statistics as Topic, Surveys and Questionnaires