20-Year Follow-Up of 7,186 Koreans: Meeting 3 Prediabetes Criteria Raises Diabetes Risk 15-Fold

Even among people with the same "prediabetes," the risk of progressing to type 2 diabetes differed greatly depending on which criteria were used to diagnose it. Researchers at Hallym University Dongtan Sacred Heart Hospital published in Diabetologia the results of following 7,186 participants (ages 40 to 69) in the Korean Genome and Epidemiology Study (KoGES) for up to 20 years.

The more criteria overlap, the higher the risk

Participants had an oral glucose tolerance test and an HbA1c test every two years. Compared with the normal-glucose group, the adjusted hazard ratios for developing diabetes were 5.84 for impaired fasting glucose (IFG), 4.60 for impaired glucose tolerance (IGT) and 4.68 for prediabetes by HbA1c criteria. Meeting just one criterion carried a ratio of 3.10, but two criteria raised it to 7.33 and all three to 15.3. People who met all three criteria spent the shortest time in prediabetes, 1.7 years, and had the lowest chance of returning to normal, 5.4%.

Apart from blood glucose levels, risk was also higher when indicators of insulin secretion capacity (insulinogenic index) or insulin sensitivity (insulin sensitivity index) were low. When both were low, the ratio was 4.06, and even among people with blood glucose in the normal range, risk rose if these indicators were low. The researchers concluded that adding insulin secretion and sensitivity information to glucose criteria makes risk stratification more precise.

These are results from a community cohort in a single country, so they are hard to apply directly to other ethnic groups or populations, and because this is an observational study, causation cannot be established.