Hierarchical structure of the activities of daily living scale in dementia.

Objectives: To describe the sequence of basic activities of daily living (ADL) loss to determine whether there is a hierarchical structure of ADL in dementia in two epidemiological prospective studies: the Paquid study and the Three City Study (3C).

Design: Two prospective population-based cohort studies: Paquid (over 22 years of follow-up) and 3C (over 10 years of follow-up).

Setting: Paquid Study, Gironde, Dordogne, France; The Three Cities Study, Bordeaux, Montpellier, Dijon, France.

Main Outcomes Measures: We analyzed four ADL of the Katz scale: bathing, dressing, transferring and feeding. The a priori hierarchical relationship of the 4 activities tested was 1) no ADL-disability at all four activities; 2) moderate ADL-disability, or disability at bathing and/or dressing (and no disability in transferring nor feeding); and 3) severe ADL-disability, or disability in bathing and/or dressing and transferring and/or feeding. We performed a Guttman scale analysis to establish the hierarchical properties scale.

Results: In total, 845 incident cases of dementia were included, among which 838 cases (99.2%) were without any missing data for ADL. Upon diagnosis of dementia, 564 subjects (67.3%) had no ADL-disability, 236 (26.2%) had moderate ADL-disability, and 38 subjects (4.5%) had severe disability. The a priori hierarchy was respected with non-discordance.

Conclusion: We defined 3 simple relevant stages of ADL functional decline in dementia that would be easy to collect in clinical practice: stage 1, subjects with no major ADL disabilities; stage 2, subjects with complete disability in bathing and/or dressing; and stage 3, subjects with complete disability in all 4 tasks.