The Heart of Diabetes
The American Diabetes Association (ADA) 60th Annual Meeting and Scientific Sessions, held in San Antonio in June, will certainly be remembered for the torrential rainstorms that repeatedly soaked attendees and wreaked havoc on airline schedules. But they should also be remembered for their emphasis on cardiovascular disease. One physician joked that he thought he was at an American Heart Association meeting instead of an ADA meeting. At least 48 abstracts presented data related to macrovascular disease. The program also included three symposia, one workshop, and four current issues sessions on cardiovascular disease. And, there were eight corporate symposia focusing on this topic.
Was this an aberration? A diabetes meeting should focus on new drugs and technologies for treating hyperglycemia, right? There are so many mental health and psychosocial issues associated with diabetes per se that one could also argue that we should be spending more of our resources on these issues. And, let's not forget the microvascular complications and associated morbidities that are seen exclusively with diabetes. The cellular mechanisms that cause these complications, population-based screening strategies, and new treatments should be identified and presented at an ADA meeting. So why the emphasis on cardiovascular disease?
The reason, quite simply, is that this problem has been ignored for too long. Cardiovascular disease, which includes coronary heart disease, cerebrovascular disease, and peripheral vascular disease, is the leading cause of mortality in people with diabetes.1 Most of these deaths are caused by coronary artery disease (CAD). Furthermore, after myocardial infarction, people with diabetes have a two- to threefold greater morbidity and mortality than those without diabetes.1 Clearly, it is time we give this problem more attention.
This year's ADA meeting was not an aberration. To test the degree to which diabetes is infiltrating the cardiology literature, articles pertaining to diabetes were reviewed in a Medline search for the journal Circulation, one of the premier cardiology journals (Figure 1). As can be seen, the number of articles in which the word "diabetes" appears in the title increased more than threefold between 1990 and 1999. Another important conclusion from this is that diabetes research funding is increasing at both the basic science and clinical levels. This is not to suggest that funding for diabetes-related cardiovascular disease research is adequate, but it does indicate that the quantity of this research seems to be going in the right direction.
One must then ask whether this increase in research is resulting in improved clinical outcomes. The answer, of course, is that we hope so, but it is too soon to tell.
One recent large survey of 1,489 patients with diabetes revealed that 22% received exercise counseling, 82% received a blood pressure measurement, and only 5% received advice to take aspirin daily.2 On the other hand, two-thirds of patients received some type of lipid-lowering medication.2 To me, these results suggest that American physicians are paying more attention to dyslipidemia but are ignoring other aspects of the treatment (especially primary prevention) of macro-vascular disease. Interestingly, the least controversial and least expensive aspects of this care (blood pressure measurement, exercise counseling, aspirin prescription) are the ones for which we have the greatest room for improvement.
To me, the most important aspect of this topic for primary care providers is deciding when to screen for CAD. In 1998, the ADA published its first consensus statement on the diagnosis of CAD in people with diabetes.3 Some people have criticized the recommendations in this document for not being "evidenced-based." Although this is true, and we do not have a cost analysis from a randomized, controlled trial to demonstrate the cost-effectiveness of CAD screening in high-risk individuals, we sometimes need to use common sense to do the right thing for our patients. For patients with diabetes, that would include screening for CAD.
While I try to follow ADA recommendations for my patients, others may want something more quantitative regarding the risks for coronary disease and screening recommendations. The British Cardiac Society, British Hyperlipidemia Association, British Hypertension Society, and British Diabetic Association recently published guidelines for aggressive blood pressure and lipid therapy based on the risk for developing cardiovascular disease over the next 10 years.4 Risks are set forth on grids based on age, diabetes status, sex, smoking status, blood pressure, and ratio of total cholesterol and HDL cholesterol.
For example, a 50-year-old woman with type 2 diabetes who smokes and has a total cholesterol of 210 mg/dl, HDL cholesterol of 30 mg/dl, and systolic blood pressure of 150 mmHg would have a 30% risk for developing CAD during the next 10 years. The authors define "high risk" as anything over a 20% risk during the next 10 years. Under the British guidelines, a provider should treat this woman's blood pressure and lipids aggressively and encourage her to stop smoking. I would extrapolate from her grid profile to conclude that she also needs to be screened for CAD.
Certainly, this type of risk grid is one way to better identify appropriate patients for coronary disease screening. I could also see using this grid as a teaching tool to help patients better understand their risks.
I suspect that at next year's ADA meeting, there will be even more opportunities to learn about cardiovascular disease. In the meantime, it has become clear that the fields of cardiology and diabetes will be difficult to differentiate as we learn more about cardiovascular disease.
1Wingard DL, Barrett-Connor E: Heart disease and diabetes. In Diabetes in America. 2nd ed. Harris MI, Ed. Bethesda, MD, National Institute of Diabetes and Digestive and Kidney Diseases (NIH publ. no. 95-1468), 1995, p. 429-48.
2Meigs JB, Stafford RS: Cardiovascular disease prevention practices by U.S. physicians for patients with diabetes. J Gen Intern Med 15:220-28, 2000.
3American Diabetes Association: Diagnosis of coronary heart disease in people with diabetes (Consensus Statement). Diabetes Care 21:1551-59, 1998.
4British Cardiac Society, British Hyperlipidemia Association, British Hypertension Society, and British Diabetic Association: Joint British recommendations on prevention of coronary heart disease in clinical practice: summary. Br Med J 320:705-708, 2000.
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