Graves hyperthyroidism and moderate alcohol consumption: evidence for disease prevention

Background We recently demonstrated that moderate alcohol consumption is associated with a considerable reduction in the risk of autoimmune hypothyroidism, similar to findings in other autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. We aimed to study a possible association between alcohol intake and autoimmune Graves hyperthyroidism. Design This is a population-based, case-control study. Methods In a well-defined Danish population (2027208 person-years of observation), we prospectively identified patients with new overt thyroid dysfunction and studied 272 patients with Graves hyperthyroidism. For each patient, we recruited four age-gender-region-matched controls with normal thyroid function (n=1088). Measurements Participants gave detailed information on current and previous alcohol intake as well as other factors to be used for analyses. The association between alcohol intake and development of hyperthyroidism was analysed in conditional multivariate Cox regression models. Results Graves patients had a lower reported alcohol consumption than controls (median units of alcohol (12g) per week: 2 vs 4, P<0 center dot 001). In a multivariate regression model, alcohol consumption was associated with a dose-dependent reduction in risk for development of overt Graves hyperthyroidism. Odds ratios (95% confidence interval) compared with the reference group with a recent (last year) consumption of 1-2 units of alcohol per week were as follows: 0 units/week 1 center dot 73 (1 center dot 17-2 center dot 56), 3-10 units/week 0 center dot 56 (0 center dot 39-0 center dot 79), 11-20 units/week 0 center dot 37 (0 center dot 21-0 center dot 65), 21 units/week 0 center dot 22 (0 center dot 08-0 center dot 60). Similar results were found for maximum previous alcohol consumption during a calendar year. No interaction was found with the type of alcohol consumed (wine vs beer), smoking habit, age, gender or region of inhabitancy. Conclusions Moderate alcohol consumption is associated with a considerable reduction in the risk of Graves disease with hyperthyroidism - irrespective of age and gender. Autoimmune thyroid disease seems to be much more dependent on environmental factors than hitherto anticipated.