Since 1990, we have reported hospital-based studies concerning Japanese patients with early-onset diabetes in our Diabetes Center, Tokyo Women's Medical University, Japan (1). Our goal is to confirm the proportion of type 1 versus type 2 diabetes in early-onset diabetes in Japan in our center with that of the Asian group in The SEARCH for Diabetes in Youth, a recent population-based study concerning the prevalence of diabetes in youth (2).

Our study consists of 4,063 Japanese patients who were initially diagnosed as having diabetes under the age of 30 years and who registered in our Diabetes Center between 1960 and 2004. Of the 4,063 patients, 1,746 (43.0%) had type 1 and 2,317 (57.0%) had type 2 diabetes based on the diagnostic criteria of the Japan Diabetes Society (3), which is identical to that of the World Health Organization. Other specific types of diabetes were excluded from the study. We divided the subjects into three groups according to age at onset of diabetes, namely, 525 patients with diabetes diagnosed from 0 to 9 years, 1,382 from 10 to 19 years, and 2,156 from 20 to 29 years, to investigate the proportion of type 1 versus type 2 diabetes in each group. The proportion of type 1 versus type 2 diabetes in the three groups was 95.0 versus 5.0%, 50.9 versus 49.1%, and 25.2 versus 74.8%, respectively.

Approximately 10% of diabetic patients who resided in the Tokyo metropolitan area were registered in our Diabetes Center (4); therefore, although our study was hospital based, we believe it reflects a general trend of a proportion of diabetes type in early-onset diabetes in Japan. The SEARCH for Diabetes in Youth showed that the proportion of type 1 versus type 2 diabetes in Asian/Pacific Islander patients from 0 to 9 and 10 to 19 years of age at onset is 86.6 versus 6.7% and 58.5 versus 40.1%, respectively (2). Not only The SEARCH for Diabetes in Youth but also our study suggests that type 2 diabetes accounts for ∼5–7% of Asian children with diabetes and that the proportion of type 2 diabetes is nearly half of all Asian adolescents with diabetes.

1.
Otani T, Yokoyama H, Higami Y, Kasahara T, Uchigata Y, Hirata H: Age of onset and type of Japanese younger diabetics in Tokyo.
Diabetes Res Clin Prac
 
10
:
241
–244,
1990
2.
SEARCH for Diabetes in Youth Study Group: The burden of diabetes mellitus among US youth: prevalence estimates from the SEARCH for Diabetes in Youth study.
Pediatrics
 
118
:
1510
–1518,
2006
3.
Kuzuya T, Nakagawa S, Satoh J, Kanazawa Y, Iwamoto Y, Kobayashi M, Nanjo K, Sasaki A, Seino Y, Ito C, Shima K, Nonaka K, Kadowaki T, Committee of the Japan Diabetes Society on the Diagnostic Criteria of Diabetes Mellitus: Report of the Committee on the Classification and Diagnostic Criteria of Diabetes Mellitus.
Diabetes Res Clin Pract
 
55
:
65
–85,
2002
4.
Yokoyama H, Okudaira M, Otani T, Sato A, Miura J, Takaike H, Yamada H, Muto K, Uchigata Y, Ohashi Y, Iwamoto Y: Higher incidence of diabetic nephropathy in type 2 than in type 1 diabetes in early-onset diabetes in Japan.
Kidney Int
 
58
:
302
–311,
2000
DIABETES CARE
2007