A fourfold difference in the incidence of type 1 diabetes between Sweden and Lithuania but similar prevalence of autoimmunity.

We investigated whether other autoimmune disorders in addition to type 1 diabetes are more common in Sweden than Lithuania, and if there are any differences in inheritance patterns of both type 1 diabetes and other autoimmune disorders. Data from 517 children in southeast Sweden and 286 children in Lithuania aged 0-15 years were included in the study. Age- and sex-matched control children were randomly selected. Information was collected by questionnaire. Of the children with diabetes in Sweden, 13.2% had a family member with type 1 diabetes compared to 7% of children with diabetes in Lithuania (P < 0.01) (OR = 2.01). No such difference was seen for other autoimmune diseases in family members of children with diabetes (Sweden 12%, Lithuania 14%, n.s.). Control children in Lithuania had family members with autoimmunity more frequently (15.3%) than control children in Sweden (7.4%, P < 0.001) (OR = 2.26). This difference was most pronounced in mothers. The Lithuanian control children had an autoimmune disease more frequently than the controls in Sweden (4.7% versus 1.5%, respectively, P < 0.001) (OR = 3.21). There seem to be environmental factors that specifically contribute to the development of type 1 diabetes, factors which are less related to the development of autoimmunity in general.