Linking extent of return to fasting state after oral glucose tolerance test to future risk of prediabetes and type 2 diabetes: Insights from the TLGS

Abstract

ABSTRACT Aims To assess the risk of difference between 2 h post‐load plasma glucose (2 h‐PG) and fasting plasma glucose (FPG) on incident prediabetes/type 2 diabetes (T2DM) among normoglycemic individuals. Methods Among 4,971 individuals aged ≥20 years, the associations of the difference between 2 h‐PG and FPG with outcomes were examined using multivariable‐adjusted Cox regression analysis. Participants were categorized into three groups: a low post‐load group (2 h‐PG ≤ FPG, as the reference group); a high post‐load group (2 h‐PG > FPG and ≥75th percentile of the difference); and a medium post‐load group (2 h‐PG > FPG and <75th percentile of the difference), which was further categorized into three groups by equal ranges. Results Over a median of 11.5 years of follow‐up, 2,331 new cases of prediabetes/type 2 diabetes and 360 cases of type 2 diabetes occurred. Greater risks of incident prediabetes/type 2 diabetes in second (9–16 mg/dL) and third (17–24 mg/dL) medium post‐load, as well as high post‐load (≥25 mg/dL) categories, were found, with hazard ratios (95% confidence intervals) of 1.26 (1.11–1.44), 1.32 (1.15–1.51), and 1.69 (1.51–1.90), respectively; the issue was more prominent among women (P for interaction = 0.005). The risk of incident type 2 diabetes was also higher for these categories. After further adjustment for the homeostasis model assessment of insulin resistance, result remained essentially unchanged. Even among individuals with low normal FPG (i.e., <90 mg/dL), ≥9 mg/dL difference between 2 h‐PG and FPG increased the risk of composite prediabetes/ type 2 diabetes. Conclusions Greater levels of 2 h‐PG as low as 9 mg/dL than FPG among normoglycemic individuals is a harbinger of prediabetes/type 2 diabetes development.

Keywords

• Post‐load plasma glucose
• Tehran Lipid and Glucose Study
• Type 2 diabetes mellitus