The association between allergy and diabetes in the Canadian population: implications for the Th1-Th2 hypothesis

T-lymphocytes may preferentially differentiate towards a Th1 subtype, which is thought to be involved in the autoimmune aspects of diabetes, or a Th2 subtype, which is thought to mediate allergic disease. The activation of one subtype is thought to inhibit the other. To determine if diabetes is less common among those with allergic disease, consistent with the postulated TH1/Th2 paradigm, we used data from the 2000-2001 Canadian Community Health Survey of those at least 12 years of age from 125,159 households. Diabetes requiring insulin was reported in 1% whether or not allergies were reported. The crude odds ratio between diabetes and allergies for the entire population was 1.06 (95% confidence interval (CI): 0.90, 1.24). Adjusted for household size, number of bedrooms, immigrant status, income adequacy, educational level, smoking status, alcohol drinking status, regular exercise, and age, there was a positive association between allergy and diabetes with an odds ratio of 1.25 (95% CI: 1.06, 1.49). These results do not provide evidence for the existence of the Th1/Th2 paradigm as a determinant of disease patterns in the general population.