Environmental factors may be of paramount importance as driving forces in the changing trend.
The incidence of Type I diabetes mellitus in children has increased worldwide over the past 50 years. This increase has occurred in rich and poor countries in Europe, Asia, the Americas and Oceania. Rapid increases in incidence in genetically stable populations eg Finland and Sardinia imply that environmental factors are of paramount importance as driving forces in this changing trend. The significance of these trends and putative aetiological factors are reviewed.