Worse pancreatic β-cell function and better insulin sensitivity in older Chinese without diabetes

Whether insulin secretion and insulin sensitivity in older Chinese differ from younger persons without diabetes has not been examined and is unknown to us.

Oral glucose tolerance test was performed in a total of 32,245 Chinese without diabetes history. Insulin sensitivity was estimated by Matsuda's insulin sensitivity index (Matsuda ISI), and insulin secretion was measured by the insulinogenic index. The insulin secretion and sensitivity were compared among three age groups: 20-39 (the young), 40-59 (the middle), and greater than or equal to 60 years (the older).

A higher proportion of postchallenge hyperglycemia (PH), both in prediabetes and in diabetes stage, was associated with older age. In the young, middle, and older age groups, the insulinogenic index median was 10.64, 8.40, and 6.67, respectively, in individuals with normal glucose tolerance (NGT); it was 8.56, 6.12, and 4.98 in individuals with prediabetes, respectively (p < .001 vs the young group). In these three age groups, the Matsuda insulin sensitivity index was 8.20, 8.39, and 8.84 in individuals with normal glucose tolerance, and it was 5.23, 5.94, and 6.33 in individuals with prediabetes, respectively (p < .05 vs the young group). These differences were independent of body mass index and waist circumference.

Older Chinese without diabetes are characterized with worse insulin secretion and better insulin sensitivity. Insulin insufficiency and insulin resistance may contribute disproportionately to abnormal glucose tolerance in people of different age.