Association between Residences in U.S. Northern Latitudes and Rheumatoid Arthritis: A Spatial Analysis of the Nurses’ Health Study
Environmental Health Perspectives, available online 25 March 2010
Verónica M. Vieira, Jaime E. Hart, Thomas F. Webster, Janice Weinberg, Robin Puett, Francine Laden, Karen H. Costenbader, and Elizabeth W. Karlson
“Background: The etiology of rheumatoid arthritis (RA) remains largely unknown although epidemiologic studies suggest genetic and environmental factors may play a role. Geographic variation in incident RA has been observed at the regional level.
“Objective: Spatial analyses are a useful tool for confirming existing exposure hypotheses or generating new ones. To explore further the association between location and RA risk, we analyzed individual level data from U.S. women in the Nurses’ Health Study, a nationwide cohort study.
“Methods: Participants included 461 incident RA cases and 9,220 controls with geocoded addresses followed from 1988-2002. We examined spatial variation using addresses at baseline in 1988 and at time of case diagnosis/censoring of controls. Generalized additive models were used to predict a continuous risk surface, smoothing on longitude and latitude while adjusting for known risk factors. Permutation tests were conducted to test for the overall importance of location and identify areas of statistically significant risk relative to the whole study area.
Results: A statistically significant area of increased RA risk was identified in the northeast U.S. (p-value=0.034). Risk was generally higher at northern latitudes and increased slightly using nurses’ 1988 locations compared to locations at time of diagnosis/censoring. Crude and adjusted models produced similar results.
“Conclusions: Spatial analyses suggest women living in higher latitudes may be at greater risk for RA. Further, RA risk may be greater for locations occurring earlier in residential histories. These results illustrate the usefulness of GAM methods in generating hypotheses for future investigation and supporting existing hypotheses.”
