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OP20 Using a latent disability structure to  explain mortality among the older  population
  1. B Pongiglione1,
  2. GB Ploubidis2,
  3. BL De Stavola1,
  4. H Kuper3
  1. 1Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
  2. 2Centre for Longitudinal Studies, Institute of Education, London, UK
  3. 3Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, UK


Background In 2001 the World Health Organisation (WHO) proposed a conceptual framework for describing functioning and disability: the International Classification of Functioning, Disability and Health (ICF). ICF conceives and organises disability as a combination of three components: Impairment, Activity and Participation. Few studies have adopted this comprehensive approach to measure disability. The object of this work is twofold: to assess the validity of the ICF framework to measure functioning and disability when it is applied to older population; and to investigate the role of disability in explaining all-cause mortality among individuals aged 50+.

Methods Data were drawn from the English Longitudinal Study of Ageing (ELSA). 9,715 subjects aged 50+ interviewed at wave 1 (2002–2003) and followed-up for about 10 years were studied. The items used to measure impairment, activity and participation were selected and agreed in double-blind by three researchers. Confirmatory factor analysis (CFA) was used to determine to what extent the ELSA data fit the three-factor WHO’s ICF framework. The association of disability with mortality was estimated using the measure of disability derived from the measurement model and applying discrete-time survival analysis in a general latent variable framework. All analyses were performed using Mplus.

Results From CFA we identified 13 items strongly associated (factor loadings >0.4) to Impairment (I), 19 to Activity (A) and 8 to Participation (P); we also identified a specific latent eyesight variable within the impairment domain, composed by three eyesight items. The second order CFA model showed that the three-factor (I, A and P) disability structure has an acceptable fit using data on a sample of older individuals (model fit: CFI = 0.945, TLI = 0.942, RMSEA = 0.042). From the discrete time survival analysis, we found strong and significant time-varying effect of disability on mortality, which persisted throughout the follow-up (OR in the first time-event equal to 3.26, p < 0.001; OR in the last time-event equal to 2.23.). Adjusting for demographic characteristics, socioeconomic factors and health-related behaviours the association was attenuated, but overall the effect of disability on mortality remained high and significant (OR in the first time-event equal to 1.94, p = 0.016; OR in the last time-event equal to 1.75, p < 0.001).

Conclusion Our work confirmed the validity of the ICF framework to capture disability among the older population and identified the more relevant factors for each component. Disability, framed in such a way, was strongly associated with mortality and the effect was quite stable throughout the course of the 10 year follow-up.

  • ageing
  • disability
  • mortality

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