The epidemiology of type 1 diabetes, a disease of as yet unknown etiology, is complex. The overall incidence rates are comparable in North America and Europe; however, this disguises some marked variations in incidence rates between countries and even within countries. Within Europe, particularly high incidence rates are found in Finland, Sweden and Sardinia. Most Asian populations have a low incidence rate. In general, the incidence of type 1 diabetes seems to be increasing with an average increase in incidence of around 3% per year. About half of all cases of type 1 diabetes are diagnosed at an age of <15 years, with an observed peak in incidence rates in children aged 10-14 years. More recently, many cases are being diagnosed in children of <5 years of age. In many high-risk populations a male excess of type 1 diabetes is seen, especially after the age of puberty.
Cases of type 2 diabetes greatly exceed those of type 1 diabetes accounting for about 85% of cases in Europe and significantly more than this in certain ethnic groups. It is predicted that the total number of people with diabetes will rise to 300 million, or maybe more, by 2025 with a preponderance of cases occurring in the developing world. In many populations there is a declining age of peak incidence with cases now being identified in children and young adolescents, especially in highly susceptible groups such as Native Americans. In North America, type 2 diabetes is highly prevalent in Native American communities such as the Pima Indians, a feature shared by the Nauru and Papua New Guinea populations of the Pacific Islands. US Hispanic, black Americans and Polynesians also exhibit high prevalence rates. In the UK, prevalence rates of 3-5% are frequently found with higher rates observed in the Asian population as reported also in the Asian subcontinent.
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