Contribution of diseases to disability: How much the choice of the disability indicator can impact the results

Abstract

Objective Studies assessing the contribution of specific conditions to disability can help policymakers decide on intervention and preventive strategies. However, the contribution of diseases may vary according to the definition and the level of disability chosen for the analyses. Here, we aimed to describe whether the contributions of diseases to disability vary considering different disability indicators with different severity level. Material/patients and methods We used data from the 2008–09 French Disability-Health survey, a cross-sectional study including 29,990 individuals living in private households, where diseases and disabilities are self-reported. We compared the contributions of 9 chronic diseases to the following disability indicators: the Global Activity Limitation Indicator (GALI), mobility limitations (restriction in carrying a bag, climbing stairs, kneeling or walking), limitations in activities of daily living (ADL) and instrumental activities of daily living (IADL). For each one, we considered a moderate and a severe level of disability. To account for comorbidities, we assessed the contribution of chronic disorders to disability by using the average attributable fraction (AAF). Results Musculoskeletal conditions were the first contributor to moderate disabilities, whatever the disability indicator. Their impact on GALI (AAF 25.4%) and mobility limitations (26.9%) was higher than on ADL (17.8%) and IADL limitations (11%). Considering severe disability, AAFs were high for GALI (19.9%) and mobility limitations (28.3%) but low for ADL (0.0%) and IADL limitations (7.2%). Neurologic had a high contribution to ADL and IADL limitations, and their impact increased with the level of severity (AAF for moderate and severe ADL limitations: 16.5% and 28.3%; for IADL: 9.4% and 13.2%). The impact of cardiovascular diseases remained stable for all disability indicators and level of severity (AAF from 9.8% for severe mobility limitations to 16.2% for severe ADL limitations). The contribution of psychiatric conditions was high for GALI and IADL limitations, but low for mobility and ADL limitations (AAF for moderate and severe GALI: 6.7% and 10.6%; for IADL: 9.5% and 7.4%). Discussion – conclusion Musculoskeletal, neurologic, cardiovascular and psychiatric diseases mainly contribute to disability in France. Their respective impact vary according to the definition and the level of disability, what should be taken into account for interpreting results.