[Hereditary background and natural history in glucose-intolerance group]

For non-obese IGT, frequency of 1st degree DM relatives was 29.9%, a rate higher than normal. NIDDM development rate was higher in IGT with family history of DM (86.9/1000 PY) than in IGT without family history (75.4/1000PY). For IGT-2 (2hr. PG > or = 170 mg/dl), the rate was higher in the group with family history (140.1/1000 PY) than that without family history (113.6/1000 PY). The odds ratio for NIDDM was 1.76 with obesity and 1.55 with family history. With regard to the natural course, plasma glucose (PG) increased slowly with rising of IRI over a long period, then PG increased suddenly without rising IRI and reached NIDDM onset. From these results, intervention trials for prevention of NIDDM are possible during long glucose-intolerance period.