Associations Between Arthritis and Change in Physical Function in US Retirees

Background: The aims of this study were to determine among retirees: the associations of arthritis with limitations in physical functions, and whether these associations changed differently with age for those with arthritis versus without arthritis. Methods: We identified retirees from the Health and Retirement Study, a nationally representative longitudinal panel study of U.S. adults >= 51 years old. We calculated incidence density ratios (IDRs) using Poisson regression modeling with generalized estimating equations to estimate the associations between arthritis and limitations in four physical function measures (large muscle tasks, mobility, activities of daily living, and instrumental activities of daily living) adjusting for age, sex, race/ethnicity, marital status, education, total household income, depression, obesity, smoking, chronic conditions, physical activity, and cohort status. We examined interaction effects between arthritis and age to determine if the rate of change in physical function differed by arthritis status across age. Results: Over 8 years (2004-2012), significantly more retirees with arthritis had limitations with large muscle tasks (IDR 2.1: 95% confidence interval 1.6, 2.8), mobility (IDR 1.6: 1.2, 2.2), activities of daily living (IDR 2.2: 1.0, 4.7), and instrumental activities of daily living (IDR 3.7: 1.9, 7.4) than retirees without arthritis. Retirees with arthritis did not develop limitations in mobility, activities of daily living, and instrumental activities of daily living at a different rate as they aged compared to those without arthritis. Conclusions: Arthritis was associated with a greater prevalence of physical function limitations. Preventing limitations caused by arthritis is a key strategy to prevent disability in retirees.