To examine the natural history of 654 high-risk subjects (340 men and 314 women) with fasting hyperglycemia (first fasting plasma glucose [FPG] level 5.6–7.8 mmol/1) who also exhibited 2-h postload glucose concentrations <11.1 mmol/1 and an FPG level <7.8 mmol/1 in a 75-g oral glucose tolerance test (OGTT). We were particularly interested in comparing the likelihood of developing type 2 diabetes for those with persistent fasting hyperglycemia (PFH), impaired glucose tolerance (IGT), and normal glucose tolerance (NGT). PFH is a relatively new definition, and those with PFH used to be defined as NGT according to WHO criteria.
Subjects were located in a 1992–1994 community-based population survey and followed up and reexamined during 1995–1996. An OGTT was used to determine who had progressed to type 2 diabetes. Risk factors predictive of subsequent progression to type 2 diabetes were determined by comparing baseline variables from the 1992–1994 survey with data of those who had or had not progressed to type 2 diabetes in 1995–1996.
Of 654 high-risk subjects screened in the baseline survey 481 (73.5%, 255 men and 226 women) were followed up. Of these, 8.1% had progressed to diabetes (4.1% progression/year, 95% Cl 2.3–5.9). Of 131 baseline IGT subjects, 17.6% progressed to diabetes (8.8% progression/year, 6.3–11.3), but only 7.4% of 95 PFH subjects (3.7% progression/year, 2.0–5.4) and 3.5% of 255 NGT subjects (1.8% progression/year, 0.1–3.0) progressed to diabetes.
The rates of progression to type 2 diabetes were lowest from the NGT subgroup, highest from the IGT group, with the PFH group in the middle, suggesting that PFH might be a transitional condition that precedes IGT and diabetes. Other significant predictors of subsequent diabetes were baseline BMI, baseline hyperuricemia, baseline FPG, and 2-h plasma glucose concentration.