“You can ‘convert’ a person with metabolic syndrome to what is essentially a nondiabetic state with diet modification and exercise,” Dr. Keilson says. “In true diabetes, though, the risk of heart disease is profound, and many physicians will go directly to pharmaceutical therapy to give their patients maximum protection.”
Even with the known benefits of diet and exercise and the existence of a variety of medicines, however, many people with diabetes are still at increased risk. At least half of the people with diabetes in the United States have total cholesterol levels above 200 mg/dl, which is the upper limit of the desirable range.
This disturbing report comes from a January 2004 review of data in the National Health and Nutrition Examination Survey 1999–2000. The review found that 51.8% of the people with diabetes in the survey had total cholesterol levels above 200 mg/dl. This was improved from a similar survey conducted between 1988 and 1994, but it means that millions are still above current cholesterol-lowering treatment goals.
The primary focus of dyslipidemia treatment in all people, with diabetes or not, is LDL cholesterol. Overwhelming evidence from clinical trials, experimental animals, laboratory research, and epidemiology points to LDL cholesterol as the form of cholesterol most likely to cause atherosclerosis.
Current standards call for lowering levels of LDL cholesterol below 100 mg/dl for people with known atherosclerosis. Diabetes is now considered a “coronary heart disease risk equivalent,” so people with diabetes are managed as if they already have atherosclerosis.
There are two ways to lower LDL levels: lifestyle changes and drug therapy. The American Diabetes Association (ADA) recommends starting diet and exercise changes if one’s LDL level is over 100 mg/dl and adding drug therapy if it exceeds 130 mg/dl. For people with diabetes who already have cardiovascular disease, however, drug therapy should be started along with lifestyle changes if their LDL levels are above 100 mg/dl.
Observational studies have concluded that people who adopt healthier diets and get more exercise have fewer heart attacks and other such cardiac events. Both diet modification and exercise have been shown to improve the dyslipidemia of diabetes, so by extension they are considered the best first-line treatment.
The ADA calls diet modification “medical nutrition therapy,” or MNT, and the American Heart Association includes it with exercise in what it calls “therapeutic lifestyle changes,” or TLC. Both recommendations call for reducing saturated fat in the diet and replacing it with an increased intake of carbohydrate or monounsaturated fat. Intensively following such a diet has been shown to result in a 15–25 mg/dl reduction in LDL levels.
“Diet and exercise can be expected to reduce LDL levels by no more than about 10%,” Dr. Keilson says. “Appropriate drug therapy, on the other hand, can bring about a 30% to 50% decrease. Exercise and diet are still important, for a variety of reasons, but the risk of heart disease is so high in people with diabetes that most should probably have drug therapy as well.”
Drugs for lowering LDL cholesterol
The first drug of choice to lower LDL cholesterol levels is usually an HMG CoA reductase inhibitor, or “statin.” These drugs, including pravastatin (brand name Pravachol), simvastatin (Zocor), lovastatin (Mevacor), fluvastatin (Lescol), rosuvastatin (Crestor), and atorvastatin (Lipitor), are well tolerated with few short-term or long-term side effects. The Heart Protection Study used simvastatin and reduced cardiovascular events by 25% in people with diabetes. (The authors of the study note that the 25% reduction was observed in people who didn’t always take their statin properly; taking simvastatin as prescribed 100% of the time, they predict, could reduce cardiac events by 33%.) Trials of the other statins have had similarly convincing results, with mean reductions in cholesterol of 20%, average reductions in the incidence of coronary artery disease of 30%, and average reductions in mortality of 29%. Statins also have the bonus effect of lowering triglycerides as much as 35% and raising HDL levels 10%. The newest statin, rosuvastatin, appears to be the most powerful of all, with significantly greater effect on all the lipids than other members of the family.