Effects of niacin on the incidence of new onset diabetes and cardiovascular events in patients with normoglycaemia and impaired fasting glucose

Background: This post hoc analysis from the Coronary Drug Project (CDP) evaluated the effects of niacin vs. placebo on the incidence of new onset type 2 diabetes mellitus (T2DM) and cardiovascular event rates in patients with normal and impaired fasting glucose (IFG). Methods: The CDP was a randomised, placebo-controlled clinical trial of lipid-modifying agents in men with previous myocardial infarction. Normoglycaemia and IFG were defined as fasting plasma glucose (FPG) <5.6mmol/l and FPG 5.6 but <7.0mmol/l, respectively. New onset T2DM was defined by 1 of the following: clinical diagnosis of T2DM, use of an antihyperglycaemic therapy, or two FPG values 7.0mmol/l. Results: The incidence of new onset T2DM was higher in patients with IFG (16.5%) compared with those with normoglycaemia (5.4%), and was slightly higher with niacin vs. placebo in both normoglycaemic (6.8% vs. 4.9%; p=0.07) and IFG (19.8% vs. 15.2%; p=0.05) patients. Consistent with previous analyses, the cardiovascular benefit of niacin was independent of baseline glycaemic status (normal, IFG, T2DM) and change in fasting glucose level from baseline to year 1. Conclusion: Despite a modest increase in risk of new onset T2DM with long-term niacin therapy, there is a potential cardiovascular benefit of niacin.