The news out of the United Kingdom in June 2003 was a call to action for people with diabetes and their physicians. Investigators in the Heart Protection Study had reported a year earlier that the drug simvastatin had lowered cholesterol levels in study subjects and reduced the risk of heart attack and stroke by 25%. The researchers then looked at the subgroup of subjects who had diabetes, and published their findings in June 2003.
They found that lowering levels of low-density lipoprotein (LDL) cholesterol (often referred to as “bad” cholesterol) by 39 mg/dl resulted in a 22% reduction in the likelihood of a first heart attack or stroke in people with diabetes. Significant cardiac benefits were found even in people who entered the study with no signs of arterial hardening and those whose LDL levels were within ranges that don’t automatically suggest the need for LDL-lowering drugs. These results led the researchers to conclude their report with a declaration that “statin therapy should now be considered routinely for all diabetic patients at sufficiently high risk of major vascular events, irrespective of their initial cholesterol concentrations.”
The relationship between heart disease and the various forms of lipids (blood fats such as cholesterol and triglycerides) was described as early as the 1930’s and confirmed in the Framingham Heart Study in the 1970’s and by many other studies since then. Cholesterol is a key contributor to atherosclerosis, the “hardening of the arteries” that leads to heart disease, stroke, and peripheral vascular disease.
This is particularly important to people with diabetes, in whom atherosclerosis is much more prevalent. Three-quarters of people with diabetes will die of complications that arise from atherosclerosis. They have a 2–4 times higher risk of heart attack and stroke and are more likely to die in the hospital undergoing a cardiac procedure. They also do less well following a heart attack or surgery. Atherosclerosis in the peripheral circulation, primarily in the arteries of the legs, is 2–4 times more likely in people with diabetes. This can lead to dangerous clots, pain, and amputation.
People with diabetes, in particular Type 2 diabetes, have a characteristic dyslipidemia (lipid disorder) that puts them at higher risk of atherosclerosis. They tend to have high blood levels of triglycerides and low levels of high-density lipoprotein (HDL) cholesterol. HDL cholesterol is often referred to as “good” cholesterol, because it appears to protect against atherosclerosis. Although people with diabetes tend to have levels of LDL cholesterol that are the same (or only slightly elevated) as people who don’t have diabetes, their LDL particles are of a different and more dangerous kind.
The LDL particles in people with diabetes are different because they contain more triglycerides. “When you increase the concentration of triglycerides in LDL cholesterol, its structure changes and it becomes a smaller, denser particle,” says Leonard M. Keilson, MD, MPH, a lipids specialist practicing in Portland, Maine. “These dense LDL particles are particularly dangerous, because they can more easily cross the endothelium — the lining of the arteries — and enter the wall of the vessels.” Fatty deposits in arterial walls lead to atherosclerosis.
Diet modification and exercise can help with this dyslipidemia, although Dr. Keilson cautions that they are most effective in people who have metabolic syndrome (a group of problems including cholesterol abnormalities, abdominal obesity, high blood pressure, and insulin resistance that increase the risk of diabetes, heart disease, and stroke) as opposed to full-blown Type 2 diabetes.