Longitudinal insights into the natural history of Type 2 diabetes among Koreans: A 20-year community-based prospective cohort study.

Abstract

To investigate the natural history of diabetes mellitus (DM) based on metabolic phenotypes of prediabetes in a community-based prospective study. Individuals aged 40-69 years without DM were followed for 20 years. Glycemic parameters, including the 75 g oral glucose tolerance test, were assessed at baseline and biennially thereafter. Markov models were used to estimate each glycemic state's annual transition probabilities and average total length of residence. Among the 7,676 participants without DM, 205 had isolated impaired fasting glucose (iIFG), and 1,753 had impaired glucose tolerance (IGT) at baseline. During the 17.5 years of follow-up, 2,313 (30.1%) cases of DM occurred. The annual transition to DM for those with iIFG was 7.7% (95% confidence interval [CI] 6.9, 8.5) and 6.9% (95% CI 6.6, 7.3) for those with IGT. In the normoglycemia ↔ iIFG → DM model, the total length in normoglycemia was 49.4 years (95% CI 47.0, 52.1), and the length in iIFG was 6.3 years (95% CI 5.9, 6.8). In the normoglycemia ↔ IGT → DM model, the total length in normoglycemia was 34.0 years (95% CI 32.4, 35.4), and the length in IGT was 11.9 years (95% CI 11.1, 12.5). Individuals remained normoglycemic for long periods. However, the progression to DM occurs rapidly once prediabetes develops, regardless of the metabolic phenotype.