What is the Risk for Coronary Heart Disease in a Type 2 Diabetic Without Other Risk Factors?

Abstract & Commentary

By Ralph R. Hall, MD, FACP, FACSM, Emeritus Professor of Medicine University of Missouri-Kansas City School of Medicine. Dr. Hall is a consultant for Aventis.

Synopsis: There is a wide variation in the rate of coronary heart disease (CHD) in diabetes, depending on the population and existing risk factors.

Source: Howard BV, et al. Coronary heart disease risk equivalence in diabetes depends on concomitant risk factors. Diabetes Care. 2006;29: 391-397.

Howard and colleagues studied the influence of single and multiple risk factors on the 10-year cumulative incidence of fatal and nonfatal CHD and cardiovascular disease (CVD) in diabetic and non-diabetic men and women, with and without baseline CHD or CVD in a population (n = 4549) with a high prevalence of diabetes.

In both sexes, diabetes increased the risk for CHD (hazard ratio, 1.99 and 2.93 for men and women respectively). Diabetic men and women had a 10-year cumulative incidence of CHD of 25.9 and 19.1%, respectively, compared with 57.4 and 58.4% for non-diabetic men and women with previous CHD. The pattern was similar when only fatal events were considered. Diabetic individuals with one or two risk factors had a 10-year cumulative incidence of CHD that was only 1.4 times higher than that of non-diabetic individuals (14%). However, the 10-year incidence of CHD in diabetic subjects with multiple risk factors was > 40%, and the incidence of fatal CHD was higher in these subjects than in non-diabetic subjects with previous CHD. Data for CVD showed similar patterns, as did separate analysis by sex.

These results and comparisons with other available data show wide variation in the rate of CHD in diabetes, depending on the population and existing risk factors. Most individuals had a 10-year cumulative incidence of > 20%, but only those individuals with multiple risk factors had a 10-year incidence of CHD that was equivalent to that of patients with CHD. The authors conclude that until more data are available, it may be prudent to consider targets based on the entire risk factor profile rather than just the presence of diabetes.

Commentary

The authors note that there are concerns regarding the specific ethnic group, variation in care that diverse groups may receive, and the use of statins, ACE inhibitors, and aspirin during the time course of this study. Still the evidence is strong that hyperglycemia without other risk factors was not associated with an increased incidence of CVD.

Grundy, in his editorial discussion of this paper adds that this is true at least over a short period of time.1 He also points out Alexander et al's report from the National Health and Nutrition Survey (NHANES) III who have concomitant metabolic syndrome (and thus multiple risk factors) have increased risk for major coronary events as compared with those without the syndrome.2

Eighty six percent of the patients with type 2 diabetes older than 50 years of age in the NHANES III had the metabolic syndrome.3 Since the vast majority of patients with type 2 diabetes have multiple risk factors, the National Cholesterol Education Program Adult Panel III (ATP III) listed diabetes as a CHD equivalent. According to Grundy they have rejected the concept that risk adjustment should be carried out on each individual. Therefore "a diagnosis of cardiovascular disease triggers a full therapeutic response for secondary prevention."1 A further justification for this approach is that having an elevated blood glucose may be associated with an increase in the number of risk factors in the future. ATP III set a goal of < 100 for LDL Cholesterol in these patients.

One paragraph in Grundy's editorial sums up the problem and the current solution. "In ATP III, CHD risk equivalent defines the risk of developing a major coronary event (myocardial infarction + coronary death) over 10 years of > 20%. The 20% risk was that of patients with stable angina who have not sustained a myocardial infarction. This risk is lower than for those who have a history of acute myocardial infarction which is about 26%."1

The cost-effective analysis by ATP III indicated that cholesterol-lowering drugs were very cost effective to a risk level of 20% or lower. Since the cost of lipid lowering drugs is rapidly declining, the cost effective level may fall below the risk level of 10%.

Not addressed by this study is the impact that a diabetic having 8 or more risk factors will have on Pay for Performance. Patients already on the edge of what they can afford may opt out of the recommendations their physicians make.4

References

1. Grundy SM. Diabetes and coronary risk equivalency: what does it mean? Diabetes Care. 2006;29:457-460.

2. National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) 2002. Circulation. 2002;106:3143-3421.

3. Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 2002;106:3143-3421.

4. Sorkin JD, et al. The relation of fasting and 2-h postchallenge plasma glucose concentrations to mortality: data from the Baltimore Longitudinal Study of Aging with a critical review of the literature. Diabetes Care. 2005;28:2626-2632.