I recall reading an article that raised the question or linked type 1 diabetes with birth month with July and August being most frequent. I believe the study was done in Sweden or Norway. Do you have any more information?

For some years now, there has been an extensive epidemiological study of childhood diabetes in Sardinia. The trigger for this has been the unexpectedly high incidence of type 1A (autoimmune) there. Dr Marco Songini was the first author about a recent study there. See Seasonality of birth in children (0-14 years) and young adults (0-29 years) with type 1 diabetes mellitus in Sardinia differs from that in the general population. The Sardinian Collaborative Group for Epidemiology of IDDM., Songini M, Casu A, Ashkenazi I, Laron Z. J Pediatr Endocrinol Metab 2001 Jun;14(6):781-3. You can view the abstract on-line, find the article in any medical library or your local librarian should be able to get a copy for you for a few dollars. It confirms what you said about a bias to the summer months.

DOB