Health-selective migration among patients with rheumatoid arthritis in Québec: a cohort study using administrative data.

Little is known about how rheumatoid arthritis (RA) affects an individual's ability to relocate. The current literature suggests the relationship between health and migration is often disease-specific. We sought to estimate the impact of RA diagnosis on migration within a Canadian province, comparing migration rates in residents before and after RA diagnosis. We identified a cohort of 81,181 individuals diagnosed with RA between 1998 and 2009 using Québec administrative databases. A migration was defined as a change in the first three characters of the postal code. We categorized migrations as urban or rural depending upon an individual's origin and destination. We estimated the association between RA diagnosis and migration by fitting marginal models using a generalized estimating equations approach, adjusting for age, sex, and population level socioeconomic status indicators. The vast majority of moves after RA diagnosis were within urban areas. RA diagnosis was associated with increased migration except for people around age 50 moving within urban areas. Although RA was associated with increased inter-urban migration in many demographic groups, the net result did not translate to higher rates of rural-to-urban migration after RA diagnosis. Our results suggest fairly complex associations between RA diagnosis and migration. Both age and location (urban or rural) modify this effect. Overall, we did not see a greater movement from rural-to-urban areas after RA diagnosis. This is of interest for studies of regional environmental effects on chronic disease patterns.