Baseline level of 30-min plasma glucose is an independent predictor of incident diabetes among Asian Indians: analysis of two diabetes prevention programmes.

BACKGROUND: The objective was to study the ability of the 30-min plasma glucose (30-min PG) during an oral glucose tolerance test to predict the future risk of type 2 diabetes among Asian Indians with impaired glucose tolerance.
METHODS: For the present analyses, we utilized data from 753 participants from two diabetes primary prevention studies, having complete data at the end of the study periods, including 236 from Indian Diabetes Prevention Programme-1 and 517 from the 2013 study. Baseline 30-min PG values were divided into tertiles: T1 < 9.1 mmol/L (<163.0 mg/dL); T2 9.2-10.4 mmol/L (164.0-187.0 mg/dL) and T3 ≥ 10.4 mmol/L (≥188 mg/dL). The predictive values of tertiles of 30-min PG for incident diabetes were assessed using Cox regression analyses
RESULTS: At the end of the studies, 230 (30.5%) participants developed diabetes. Participants with higher levels of 30-min PG were more likely to have increased fasting, 2-h PG and HbA1c levels, increased prevalence of impaired fasting glucose and decreased beta cell function. The progression rate of diabetes increased with increasing tertiles of 30-min PG. Cox's regression analysis showed that 30-min PG was an independent predictor of incident diabetes after adjustment for an array of covariates [Hazard Ratio (HR):1.44 (1.01-2.06)]
CONCLUSIONS: This prospective analysis demonstrates, for the first time, an independent association between an elevated 30-min PG level and incident diabetes among Asian Indians with impaired glucose tolerance. Predictive utility of glycemic thresholds at various time points other than the traditional fasting and 2-h PG values should therefore merit further consideration.