The association between allergy and rheumatoid arthritis in the Canadian population

Background: Antagonism between Th1 and Th2 lymphocyte mediated responses has been proposed to explain the observed 20th Century population increase in Th2 mediated allergic disease and reciprocal decrease in infectious disease, which stimulates a Th1 mediated response. Objective: To determine if Th1/Th2 antagonism would be consistent with associations between non-infectious diseases, we tested the hypothesis that the population prevalence of Th2 mediated allergies is inversely related to the prevalence of Th1 mediated rheumatoid arthritis. Methods: The analysis was based on data from the Canadian Community Health Survey conducted by Statistics Canada in 2000-2001 of those at least 12 years of age from 125,129 households. Each subject was asked if he or she had certain chronic health conditions that had been diagnosed by a health professional. Logistic regression models were used to evaluate the association between rheumatoid arthritis and allergies with consideration of other important variables. Results: Allergy history was positively related to the prevalence of rheumatoid arthritis both in women (adjusted odds ratio (OR): 1.57, 95% CI: 1.43, 1.73) and in men (adjusted OR: 1.55, 95% CI: 1.36, 1.77). Conclusions: The reported population prevalences of allergies and rheumatoid arthritis were positively associated and not explained by Th1/Th2 anatagonism suggesting that this mechanism may only be applicable to the association between an infectious and an immunologic disease. Mechanisms accounting for positive associations between immunologic diseases deserve further study.