An assessment of the construct validity of the descriptive system for the ICECAP capability measure for older people

BACKGROUND: The index of capability (ICECAP) was developed using in-depth interviews with 40 older people and comprises five attributes: attachment, security, enjoyment, role and control. This paper explores the construct validity of these five capability attributes. METHODS: An interview survey was conducted with individuals aged 65 and over located across the UK. Data were analysed in six categories (socio-demographic variables and general well-being, contact with others, health, nature of the locality and environment, social support and participation) using chi-squared tests (for categorical variables) or one-way analysis of variance (for continuous variables). RESULTS: About 315 individuals were interviewed (response rate 66%). Relationships were generally as anticipated with, for example: strong relationships between age and capability and well-being and capability, but no relationships between capability and either sex or social class; strong relationships between physical measures of health and role, enjoyment and control, and between mental health measures and attachment and enjoyment. CONCLUSIONS: This study provides some early evidence for the construct validity of the ICECAP measure. Where anticipated relationships were not observed this might in part be explained in that the ICECAP index asks about capability, but the factors with which associations were examined were largely and inevitably measures of function.