Is borderline fasting hyperglycemia a risk factor for cardiovascular death?

The majority of previously reported studies of borderline hyperglycemia as a risk factor for cardiovascular disease are based on post-challenge glucose levels, are limited to men, and show either no significant association or a possible threshold effect. In order to determine whether fasting plasma glucose (FPG) in the normal range (less than 140 mg/dl) predicts mortality, we prospectively studied a geographically defined Southern California community of 3625 nondiabetic men and women aged 40-79, 99.5% of whom were followed for 9 years. Levels of FPG were significantly associated with levels of most heart disease risk factors. After adjusting for these risk factors, FPG, analyzed either as a continuous or categorical variable, was independently and significantly associated with all-cause, cardiovascular and ischemic heart disease mortality in men in proportional hazard models. An excess of all-cause mortality with the highest levels of FPG (130-139 mg/dl) was the only statistically significant association seen in women. The absence of a significant linear association in women may reflect true sex differences or a lack of power owing to the relatively small numbers of deaths in women. The independent linear glucose mortality association in men found here differs from previous studies, and may reflect both the larger number of events and the use of FPG, which has less intra-individual variability and less potential for misclassification bias than post-challenge glucose.