Do Activities of Daily Living Have a Hierarchical structure? An Analysis of 5 Taiwan Elderly Population Datasets

General acceptance of a patterned progression of dependency in activities of daily living (ADL) has led to the widespread practice of simply counting the individual's basic ADL independence to reflect his or her self-care needs and impairment level. This study, based on 5 datasets which were built from 1990 to 1994 and contains health status data of 2800 persons aged 55 years and older who lived in the community or long-term care institution in Taiwan, is to uncover the dimensional structure of a set of disability items of activities of daily living (ADL) by factor analysis, and to assess the hierarchical relationship of physical ADL (PADL) factor by Guttman’s scaling procedure. Results of the analyses indicate that ADL scale does reveal two distinct dimensions-- physical ADL and instrumental ADL as well as, but not better than, the original Katz's ADL scale and Lawton & Brody's IADL scale; and that the hierarchical order is not the same as the original hypothesis of Katz's ADL, although PADL strictly meets the requirement of Guttman’s scale