Background and objective: We examined the reliability and validity of self-reported limitations encountered in the activities of daily living (ADL) as measure of functional performance, for Turkish, Moroccan, and indigenous Dutch elderly in the Netherlands.
Methods: We obtained data on self-reported ADL measured by Katz' ADL index and on five related health outcomes among a general population sample of 304 Dutch, 330 Turkish, and 299 Moroccan respondents aged 55-74 years, in Amsterdam, the Netherlands (response: 60%).
Results: Katz' ADL index demonstrated good internal consistencies for each ethnic group (Cronbach's alphas: 0.84-0.94). Regarding validity, the ADL index showed relatively strong associations with related outcomes, that is, long-term limitations in mobility and SF-36 physical functioning (rank correlations: 0.64 and -0.60, respectively). Associations with more general health outcomes, number of chronic disorders, Center for Epidemiologic Studies-Depression scale symptoms, and SF-36 role performance were weaker, as expected. Associations were stronger for Moroccans than for indigenous Dutch elderly regarding both SF-36 outcomes and depressive symptoms.
Conclusion: Katz' ADL index is valid to assess functional performance of Turkish, Moroccan, and Dutch elderly, but comparisons with Moroccan elderly should be handled with caution. The explanation of these findings and their generalizability to other ethnic groups deserve further study.