Body Composition and Disability in RA and SLE

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The overarching aim of this study is to estimate the role of body composition in the development of functional imitations and disability in both rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), within the context of a well-established model of disablement. Use of this model will facilitate a greater understanding of the role of body composition in the development of disability, taking into account other disease, therapeutic, demographic, psychosocial, and behavioral factors that may contribute to or protect from disability. This project also represents the first attempt to characterize disability among persons with SLE across a wide range of life activities using the "valued life activities" model of disability. Specific aims are to: (1) examine the role of body composition in development of functional limitations and disability in SLE and RA, using an existing model of disablement; (2) identify risk and protective factors that interact with body composition in the development of functional limitations and disability, or the maintenance of function and avoidance of disability, in RA and SLE; and (3) estimate the prevalence and incidence of disability in a wide range of life activities in a large group of individuals with SLE. Subjects for the proposed study will be members of the existing UCSF RA Panel and Lupus Outcomes Study (LOS). Existing study protocols include annual telephone interviews with the cohorts through 2008, with an additional two years proposed in the Methodology Core of this application. The proposed study will build upon this by adding project-specific measures to the annual telephone interviews, and adding two in-person assessments at the UCSF General Clinical Research Center (GCRC) for a subset of subjects from each cohort. At the GCRC visit, we will conduct an assessment of body composition, conduct testing of muscle strength and physical function, obtain blood samples for measurement of inflammatory and other markers, obtain an estimate of habitual physical activity, and perform a cognitive function evaluation. Analyses, combining interview and home visit data, will focus on 3 major areas - (1) describing body composition findings in the 2 cohorts, (2) estimating the relationship between body composition and functional limitations and disability in the 2 cohorts; and (3) identification of factors that may modify or mediate the relationship between body composition and either functional limitations or disability. Analyses will also identify the correlation between self-reported information from interview data (e.g., body mass index calculated from self-reported height and weight) with that gathered from the GCRC assessment. The findings from this study will provide information that can assist in identifying individuals with RA and SLE who may be at greatest risk of disability, and estimating the effect of intervening factors on the development of disability.