Type 2 diabetes patients had a greater likelihood of having an acute myocardial infarction if they were treated with human neutral protamine hagedorn (NPH) insulin than if they were treated with insulin glargine, according to findings from a large retrospective study published online in the American Journal of Cardiology.
The results should be interpreted cautiously, noted the study's lead author Dr. George G. Rhoads, of the University of Medicine and Dentistry of New Jersey School of Public Health in Piscataway, and his associates.
However, they do “raise the possibility that specific insulin formulations or regimens might confer different levels of risk of [acute myocardial infarction] in patients with type 2 diabetes mellitus, and that this effect might be independent of the intensity of glucose control,” they wrote (Am. J. Cardiol. 2009;104:910-6).
The investigators culled data from the Integrated Health Care Information System, a large administrative database involving enrollees of more than 30 U.S. managed health care plans.
All the inpatient claims analyzed were for acute MIs among patients who were taking oral antidiabetic agents after initiation of either NPH, a basal insulin (5,461 patients), or insulin glargine, a newer, long-acting synthetic insulin analogue (14,730 patients). Their mean age was 56 years.
In the NPH group, significantly more patients were women and the rates of baseline comorbidities, medical claims for hypoglycemia, and medical service use for diabetes were higher, but the rates of hypertension, hyperlipidemia, and statin use were lower. The average adjusted hemoglobin A1c was about 8% in the two groups.
During a mean 2-year follow-up period after initiating insulin treatment, the risk of an acute MI was 56% greater in the NPH group than in the glargine group.
Among the possible mechanisms that might help explain the difference was a higher rate of hypoglycemic events, according to the investigators; however, after adjustment for such events, the association did not change significantly.
There is a paucity of information on the cardiovascular safety of injectable insulin agents; and the long-term safety of NPH insulin has not been compared with that of the newer synthetic insulins.
The study was sponsored by Sanofi-Aventis, the manufacturer of insulin glargine. Dr. Rhoads has served as a consultant to Sanofi-Aventis; other authors have served as speaker, adviser, and consultant for the company.