Age‐dependent decline in β‐cell function assessed by an oral glucose tolerance test‐based disposition index

We evaluated age‐dependent changes in β‐cell function as assessed with an oral glucose tolerance test (OGTT)‐based analog of the disposition index (oral disposition index). A total of 110 Japanese normoglycemic subjects (aged 22–59 years) was divided into decadal age groups (20, 30, 40 and 50 s) and subjected to an OGTT. The oral disposition index was calculated as the product of the Matsuda index and the ratio of the area under the insulin curve to the area under the glucose curve for 0–120 min during the OGTT (AUC(ins/gluc120)). Although indexes of insulin secretion, including AUC(ins/gluc120) and the insulinogenic index, did not differ among age groups, the oral disposition index differed significantly among decadal ages and declined with age. The oral disposition index is thus a sensitive measure of β‐cell function, and a natural decline in such function likely begins in early adulthood and progresses with age. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00099.x, 2011)