Poor control of glycemia among patients with diabetes mellitus has been shown to increase the risk of cardiovascular disease. A recent study showed that intensive glycemic control can slow the progression of atherosclerosis. Guidelines for the diagnosis of diabetes are based on the minimum blood glucose levels that result in microvascular complications. The threshold of blood glucose levels may be different when considering the risk for cardiovascular disease. It is unclear what impact sex and age have on nondiabetic hyperglycemia and cardiovascular disease, and if glycemia is an independent metabolic risk factor or a confounding factor with other known cardiovascular risk factors (e.g., hypertension, obesity). Levitan and associates conducted a systematic review and meta-analysis of prospective studies to determine if nondiabetic hyperglycemia is an independent risk factor for cardiovascular disease.
The authors searched MEDLINE and the National Institute of Health Computer Retrieval of Information on Scientific Projects for articles related to blood glucose and cardiovascular disease. They identified 38 studies that included incidence of, or mortality caused by, cardiovascular disease as an endpoint; measured the blood glucose levels prospectively; and reported the relative risk (RR) and information needed to calculate the variance. Data extracted from the articles included participant’s age and sex, study duration, cardiovascular disease outcomes, range of blood glucose levels, relative risks, and confidence intervals or P values. The authors calculated pooled RR and 95% confidence intervals using a random effect model.
Of the 38 studies identified, 29 compared the highest category of glycemic control with the lowest. These studies included 194,658 participants; a mean follow-up of 12 years; and more than 6,500 cardiovascular events. Thirteen studies reported various postchallenge glucose levels, 18 reported fasting levels, five reported casual levels, and three reported A1C levels.
The group with the highest postchallenge blood glucose levels had a 27 percent increased risk for cardiovascular disease when compared with the group with the lowest levels. Regardless of the type of blood glucose assessment used, the results were similar when combining all the studies. The RR was 1.26 when patients who met the current standards for diagnosing diabetes were excluded from the analysis. After adjusting for other cardiovascular risk factors, the RR was still elevated. The RR also was higher in women than in men.
The authors conclude that blood glucose level is a risk factor for cardiovascular disease in healthy individuals without diabetes. This may be more important in women than it is in men.