Background: To investigate the role of infectious diseases in the development of type 1 diabetes, this study estimated the relative risks of type 1 diabetes immediately after infectious diseases.
Research design and methods: A case-crossover design was employed. Information on infectious diseases during 407 d before the onset of type 1 diabetes was collected from medical records and parents' interviews for 260 patients in Chinese type 1 diabetes registry. The frequency of infectious diseases in 42 d before the onset of type 1 diabetes was compared with either the usual frequency of infectious diseases over the past year or the actual frequency of infectious diseases in a comparable 42-d control period.
Results: Forty-eight (18%) patients were reported to have infectious diseases during this period based on medical records and interviews with parents. The relative risk of type 1 diabetes onset was markedly elevated to 10.1 (5.6, 17.9) immediately after infectious diseases, suggesting the role of infections as a precipitator. The relative risk decreased gradually before and after 42 d and was similar between male and female patients.
Conclusion: The results showed that infectious diseases are associated with a large and transient increase in the risk of type 1 diabetes during 42 d after the infection.