Outcome of glucose tolerance condition in patients with normal glucose tolerance with either persistently high or low 1-h postchallenge glucose levels in 75 g oral glucose tolerance test

This study aimed to investigate whether persistently high 1-h postchallenge glucose (PG) levels in a 75 g oral glucose tolerance test (75 g OGTT), as well as persistently low 1-h PG levels, are a risk factor for reclassification from normal glucose tolerance (NGT) into impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) among participants continually observed for 11 years. This single-center retrospective study used the electronic records of all participants undergoing Ningen Dock (health checkup) at Kiryu Kosei General Hospital between 2008 and 2018. In 2008, 361 of 523 participants who received Ningen Dock had NGT. Of the 361 participants, 109 received 75 g OGTT yearly for 11 years (2008–2018), and 72 of these 109 participants showed either persistently high 1-h PG (> 155 mg/dL) or persistently low 1-h PG (< 155 mg/dL) levels. These 72 participants with NGT were analyzed to observe the 1-h PG effect on glucose tolerance alteration for 11 years. They were divided into persistently low 1-h PG (N = 50) and persistently high 1-h PG (N = 22) groups. In the low 1-h PG group, 49 participants remained to have NGT, and the remaining 1 was reclassified as having IGT. In the high 1-h PG group, 8 remained to have NGT, whereas 10 and 4 were reclassified as having IGT and T2DM, respectively. High 1-h PG levels may be a risk factor for reclassification from NGT into IGT or T2DM, but not the low 1-h PG levels.