Diabetes mellitus defined by hemoglobin A1c value: Risk characterization for incidence among Japanese subjects in the JPHC Diabetes Study

Aims/Introduction: Although several risk factors for type 2 diabetes have been identified, most of them have been identified in studies on Western populations, and they should be evaluated in a Japanese population. In 2010, new diagnostic criteria for diabetes mellitus using hemoglobin A1c (HbA(1c)) were released and its use in epidemiological studies has many advantages. The aim of the present study was to evaluate risk factors for type 2 diabetes defined based on HbA(1c) values in a Japanese population. Materials and Methods: A total of 9223 subjects (3076 men and 6147 women) were followed up for 5 years. Diabetes was defined based on self‐report or HbA(1c) value. Risk factors for diabetes were evaluated as odds ratios adjusted for potential confounding factors by logistic regression. Results: During the 5‐year follow‐up period, we documented 518 incident cases of diabetes (232 men and 286 women). Of the 518 incident cases, 310 cases were diagnosed by HbA(1c) alone. Among the men, age, smoking (both past smoking and current smoking) and family history of diabetes significantly increased the risk of diabetes. Among the women, body mass index, family history of diabetes and hypertension significantly increased the risk of diabetes. These results did not change markedly after adjustment for the baseline HbA(1c) values, and the baseline HbA(1c) value itself was a significant risk factor for diabetes mellitus. Conclusions: Known risk factors for diabetes established in Western populations also increased the risk of diabetes in a Japanese population defined on the basis of HbA(1c) values. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00119.x, 2011)