Objective - To investigate whether the risk for autoimmune diabetes in adults differs between socioeconomic groups, and to compare such risk with that for type 2 diabetes.
Research Design and Methods - The inhabitants of the Norwegian county of Nord-Trøndelag were investigated by questionnaires and clinical examinations on three occasions during 1984-2008. We used information from a subset consisting of 56,296 subjects (participating in at least two surveys), including 122 incident cases of autoimmune diabetes in adults (age ≥35 and anti-GAD positive) and 1,555 cases of type 2 diabetes (age ≥35 and anti-GAD negative). Hazard ratios (HR) of diabetes associated with self-reported education and occupation were estimated by Cox proportional hazards models.
Results - High levels of education (university vs. primary school) were associated with an increased risk of autoimmune diabetes (HR 1.98, 95% CI 1.21-3.26), after adjustment for BMI, lifestyle factors and family history of diabetes. Cases with high levels of education had lower levels of C-peptide, tended to have higher levels of anti-GAD, and were more often treated with insulin. Conversely, these subjects had a reduced risk of type 2 diabetes (HR 0.69, 95% CI 0.57-0.82), a risk that was partly explained by lower BMI and more physical activity (adjusted HR 0.89, 95% CI 0.74-1.06).
Conclusions - High levels of education are associated with an increased risk of autoimmune diabetes in adults, a finding that may be mediated by effects on autoimmune activity. Since the association is not explained by traditional risk factors, other, currently unidentified, environmental factors are likely to be involved.
- Received June 4, 2010.
- Accepted October 1, 2010.
- Copyright © American Diabetes Association