A hierarchical model of domains of disablement in the elderly: a longitudinal approach

Purpose. the aims of this paper are to verify that a hierarchical relationship exists between the concepts of Activities of Daily Living (ADL), Instrumental Activities of Daily Living (IADL) and mobility and to use this hierarchical model to describe the evolution of disability. Methods: 3751 elderly community dwellers were followed-up 3 and 5 years after baseline interview. A hierarchic disability scale was computed by summing up the number of domains (ADL, IADL, mobility) in which a subject was dependent. Coefficients of scalability and reproducibility of the scale were computed. The hierarchic scale was used to describe transitions between states at each follow-up. Results: the hierarchical model fitted 99.3% of the subjects at baseline. At each follow-up most transitions were towards contiguous grades of disability in survivors, whatever their age. There was a significant trend towards increasing disability. Death rates were higher in subjects aged 75 and over, whatever their disability level. The patterns of evolution differed according to gender. Conclusions: the cumulative disability scale can be used to describe the evolution of disability with time in elderly community dwellers.