Abstract
Background: Immune system dysfunction may be associated with eating disorders, and associations could have implications for detection, risk assessment, and treatment of both autoimmune diseases and eating disorders. However, questions regarding the nature of the relationship between these two disease entities remain. We evaluated the strength of associations for the bidirectional relationships between eating disorders and autoimmune diseases.
Methods: In this nationwide population-based cohort study, Swedish registers were linked to establish a cohort of more than 2.5 million individuals born in Sweden between January 1, 1979 and December 31, 2005 and followed-up until December 2013. Cox proportional hazard regression models were used to investigate: 1) subsequent risk of eating disorders in individuals with autoimmune diseases; and 2) subsequent risk of autoimmune diseases in individuals with eating disorders.
Results: We observed a strong, bidirectional relationship between the two classes of illness indicating that diagnosis in one illness class increased the risk of the other. In women, autoimmune disease diagnoses increased subsequent hazard of anorexia nervosa, bulimia nervosa, and other eating disorders. Similarly, anorexia nervosa, bulimia nervosa, and other eating disorders increased subsequent hazard of autoimmune diseases. The gastrointestinal-related autoimmune diseases celiac disease and Crohn's disease showed a bidirectional relationship with anorexia nervosa and other eating disorders. Psoriasis showed a bidirectional relationship with other eating disorders. Prior type 1 diabetes increased risk for anorexia nervosa, bulimia nervosa, and other eating disorders. In men, we did not observe a bidirectional pattern, but prior autoimmune arthritis increased risk for other eating disorders.
Conclusions: The associations between eating disorders and autoimmune diseases provide additional support for previously reported associations. The bidirectional risk pattern observed in women suggests either a shared mechanism or a third mediating variable contributing to the association of these illnesses.
