Effects of niacin on glucose levels, coronary stenosis progression, and clinical events in subjects with normal baseline glucose levels (<100 mg/dl): a combined analysis of the Familial Atherosclerosis Treatment Study (FATS), HDL-Atherosclerosis Treatment Study (HATS), Armed Forces Regression Study (AFREGS), and Carotid Plaque Composition by MRI during lipid-lowering (CPC) study.

Although the effect of niacin on the glucose levels in subjects with diabetes mellitus has been investigated, niacin's effects on the glucose levels and atherosclerosis in subjects with normal glucose levels have not been well established. We examined the effect of niacin on the glucose levels, coronary stenosis progression using quantitative coronary angiography, and clinical events in 407 subjects who had a baseline glucose level <100 mg/dl and were enrolled in the Familial Atherosclerosis Treatment Study (FATS), HDL-Atherosclerosis Treatment Study (HATS), Armed Forces Regression Study (AFREGS), or Carotid Plaque Composition by MRI during lipid-lowering (CPC) study testing active niacin therapy. Although the fasting glucose levels increased significantly within 3 years in both subjects treated with niacin (from 85.6 ± 9.5 to 95.5 ± 19.7 mg/dl, p <0.001) and without niacin (from 85.2 ± 9.6 to 90 ± 17.9 mg/dl, p = 0.009), those treated with niacin had a significantly larger increase in glucose levels than those not taking niacin (9.88 vs 4.05 mg/dl, p = 0.002). Overall, 29% of subjects developed impaired fasting glucose within 3 years. Incident impaired fasting glucose was significantly more likely to be observed in subjects treated with niacin than in those who were not. However, the frequency of new-onset diabetes mellitus did not differ significantly between the 2 groups (5.6% vs 4.8%, p = 0.5). Niacin-treated subjects compared to untreated subjects had significantly less change in mean coronary stenosis (0.1 ± 0.3% vs 2 ± 12%, p <0.0001) and less major cardiovascular events (8% vs 21%, p = 0.001). In conclusion, the use of niacin for 3 years in subjects with normal baseline glucose levels was associated with an increase in blood glucose levels and the risk of developing impaired fasting glucose, but not diabetes mellitus, and was associated with a significantly reduced incidence of coronary stenosis progression and major cardiovascular events.