T1D is the second most common chronic childhood disease. The only disease with a higher prevalence in children is asthma. It has been estimated that approximately 20 million people worldwide have T1D.

The peak age at onset of T1D is around the time of puberty, and generally occurs earlier in girls than in boys. Although T1D is generally diagnosed in children and young adults, it can occur at any age. More is known about the epidemiology of diabetes in children compared to adults because it has been easier to identify and study affected children (e.g., ascertained through pediatricians) than affected adults, who are treated by a variety of medical specialists, including primary care physicians, endocrinologists, out patient clinics, etc.

The incidence of T1D is increasing around the world at a rate of about 3% per year, reasons for which are currently unknown. This trend appears to be most dramatic in the youngest age groups, and is completely unrelated to the current increase in T2D in children. Researchers have speculated about possible environmental changes (e.g., air pollution, improved hygiene, infant feeding patterns) that may explain the rising incidence. These increasing T1D incidence is unlikely to be due to genetic changes, because it takes many generations to alter population gene frequencies. Additional re\search is needed to determine why the incidence of autoimmune T1D is increasing worldwide.