Prevalence and age of onset of type 1 diabetes in adult Asians in the Coventry Diabetes Study.

Although Asians are known to have an excess of Type 2 diabetes when compared with Europids, the relative prevalence of Type 1 diabetes in Asians remains controversial. The Coventry Diabetes Study enumerated all adult diabetic subjects in the electoral ward of Foleshill (population 10,304) by a house-to-house survey. Residents treated with insulin were classified as having either Type 1 or Type 2 diabetes on the basis of plasma C-peptide concentration and their diabetic history. Insulin treatment was received by 22% of Europids and 12% of Asians with previously diagnosed diabetes. Diabetic history was available for all and C-peptide for 69% of insulin-treated subjects. The age adjusted prevalence of Type 1 diabetes was 0.16 (95% CI 0.6-3.3)% in Europids and 0.12 (95% CI 0.4-2.7)% in Asians. Asians were found to have a significantly higher age at diagnosis (26 (range 19-34) vs 18 (6-29) years, p less than 0.05) than Europids, and all were born outside of the United Kingdom. No Type 1 diabetes was diagnosed under 19 years of age in Asians while 5 of the 8 Europid subjects with Type 1 diabetes were diagnosed under this age. Type 1 diabetes does occur in Asians born outside the UK but either commences later in life or, if of earlier onset, precludes migration to the UK.