LOS ANGELES – Aggressive control of blood pressure, lipids, and hemoglobin A1c in Americans with type 2 diabetes would prevent nearly 1 million fatal and nonfatal myocardial infarctions and sudden cardiac deaths over 10 years.
A less aggressive approach – one that brings those risk factors to guideline-recommended targets but no further in patients not currently at goal – would still prevent more than 600,000 coronary heart disease (CHD) events, according to the first study to estimate the population-wide impact of achieving composite control of these major risk factors in the U.S. type 2 diabetic population.
Dr. Nathan D. Wong
The key to achieving preventive success on this enormous scale is to attain composite risk factor control, Nathan D. Wong, Ph. D., stressed at the annual scientific sessions of the American Heart Association.
"One of the things that needs to be emphasized is we have to have a coordinated approach, where people are taking care of all of their risk factors. All too frequently, we might take care of A1c but the blood pressure and lipids are not well controlled, or vice versa," said Dr. Wong, professor of medicine and director of the University of California, Irvine, Heart Disease Prevention Program.
"In another recent paper we did [Diab. Vasc. Dis. Res. 2012;9:146-52], we showed that less than 13% of the U.S. diabetic population is in simultaneous control of blood pressure, A1c, and lipids, so we still have a long way to go in terms of getting our diabetic patients to goal," he added.
In the study he presented at the meeting, Dr. Wong and his coinvestigators extrapolated from weighted, nationally representative data for 2007-2008 on 384 adults with type 2 diabetes and no history of CHD or stroke, in order to create a portrait of the cardiovascular risk factor status of 9.6 million such U.S. patients. The data came from the U.S. National Health and Nutrition Examination Survey (NHANES).
Next the investigators utilized the U.K. Prospective Diabetes Study risk engine version 1.1 to estimate the group’s 10-year risk of CHD events as-is. They then examined the impact of improved control of blood pressure, HbA1c, high-density lipoprotein, and total cholesterol by recalculating 10-year risk based upon better risk factor numbers.
The baseline 10-year risk of CHD events, defined conservatively as fatal or nonfatal acute MI or sudden death, was calculated at 23% in U.S. type 2 diabetic men and 12.1% in women. This translated to a projected 1.7 million CHD events among 9.6 million individuals over 10 years if their risk factor status remained unchanged.
However, the investigators projected that by controlling these risk factors to goal – that is, an HbA1c of less than 7.0%, systolic blood pressure of 130 mm Hg, total cholesterol of 170 mg/dL, and HDL of 40 mg/dL in men and 50 mg/dL in women – then 32% of CHD events in men and 39% in women would be prevented. That translates to a projected 618,100 fewer major CHD events in this population. For this study, a total cholesterol of 170 mg/dL served as a proxy for an LDL cholesterol of 100 mg/dL.
Moreover, aggressive risk factor control, defined by Dr. Wong and his coworkers as a 50% reduction from baseline in total cholesterol, a 20% increase in HDL, and a 20% decrease in systolic blood pressure, combined with an absolute 2% reduction in HbA1c, was projected to prevent 51% of CHD events in men and 58% in women with type 2 diabetes. That’s 937,320 fewer CHD events over 10 years.
Session cochair Dr. Martin K. Rutter commented, "It’s a very positive message, I think, that medical therapy has potentially such great good to do. We sometimes forget how much good we can do with our simple tools in the clinic."
Also, because the UKPDS was conducted in an era before modern aggressive risk factor reduction became common, the risk engine may actually underestimate the true value of this intensified approach in terms of preventable CHD events, said Dr. Rutter, a diabetologist at the University of Manchester (U.K.).
Dr. Wong agreed. He added that there are a couple of other reasons to think the UKPDS research engine may have undervalued the true impact of simultaneous risk factor control. For one, the investigators didn’t include the implications of smoking cessation in their calculations.
Also, NHANES did not record whether participants had atrial fibrillation, so Dr. Wong and his coworkers were forced into making risk calculations based on the false assumption that atrial fibrillation was nonexistent in the type 2 diabetic population. In reality, of course, the presence of this common arrhythmia in type 2 diabetic individuals further increases their cardiovascular risk, and thus the benefits of risk factor reduction would become magnified.