Environmental Factors Contribute to Type-1 Diabetes Risk

The worldwide incidence of type-1 diabetes is rising by 3 to 5% annually, and genetic factors fail to fully explain this trend.  Two major hypotheses have been proposed to account for possible environmental influences. The hygiene hypothesis suggests that improvements in hygiene and living conditions have led to fewer early-life infections, resulting in modulation of the developing immune system and increased susceptibility to autoimmune diseases such as type-1 diabetes.  Secondly, the overload or accelerator hypothesis proposes that overload or stress on developing pancreatic beta cells predisposes them to autoimmunity and apoptosis.  As such, Marisa A. D’Angeli, from Washington State Department of Health (Washington, USA), and colleagues explored whether the hygiene hypothesis and/or overload (accelerator) hypothesis could readily be associated with type-1 diabetes as a contributing risk factor.  The team analyzed data collected on 1,852 children younger than 19 years of age residing in the state of Washington who were hospitalized for type 1 diabetes, matching them to a group of non-diabetic controls based on age.  Supporting the hygiene hypothesis, the researchers found that those children who were hospitalized with a diagnosis of type-1 diabetes were less likely to have three or more older siblings.  The researchers observed a greater odds of type-1 diabetes among infants of mothers whose body mass index (BMI) was 30 or higher, or whose prepregnancy weight was 200 lbs or more, suggesting that overnutrition may cause overload or stress to the developing pancreas, thus supporting the overload hypothesis.  Summarizing that: “Consistent with the hygiene hypothesis, type 1 diabetes was negatively associated with having older siblings … and related to the overload hypothesis, maternal body mass index of 30 or higher was associated with increased risk of diabetes,” the team concludes that: “Environmental factors related to decreased antigenic stimulation in early life and maternal obesity may be associated with type 1 diabetes.”