Seasonality of birth in children with diabetes in Europe: multicentre cohort study. European Diabetes Study Group.

There is increasing evidence that environmental factors in early life, particularly viral infections, influence the risk of developing type 1 (insulin dependent) diabetes. The high incidence of diabetes in the congenital rubella syndrome suggests that intrauterine infection may be important, and the high incidence of enteroviral infection during pregnancy in the mothers of children who subsequently develop type 1 diabetes suggests that other viruses may also be involved. Since most common viral infections are seasonal, if a significant proportion of cases of childhood diabetes were caused by intrauterine infection it might be expected that the pattern of dates of birth of affected individuals would be abnormal. We previously reported abnormal seasonality of birth in three large independent populations of children with type 1 diabetes in the United Kingdom, and a similar pattern has since been reported in the Netherlands. To determine whether regional variation in seasonal patterns of birth of children with diabetes might provide clues to the aetiology of the disease we studied 20 cohorts of children with diabetes from 16 European countries.