Almost everyone knows that having too much "bad" cholesterol in your blood puts you at risk for heart disease. But not everyone with a high level of such low-density lipoprotein (LDL) suffers a heart attack or a stroke, and many people with normal LDL do. Indeed, only 50% of people with coronary artery disease have high levels of LDL or any other risk factor.
Research suggests this might be because the standard cholesterol screening tests measure only the percentage of LDL in your bloodstream -- when it's the size and number of LDL particles that are important. Although further study is required to decide for sure, many doctors are convinced that getting a more thorough cholesterol test, one that identifies the types of particles, can improve treatment and save lives.
BAD VS. GOOD
LDL is a molecule that transports the "bad" cholesterol. It's bad because it tends to get stuck in arteries and cause blockages. High-density lipoprotein (HDL) carries the "good" cholesterol, which mops up bad cholesterol and takes it to the liver for disposal. LDL and HDL particles come in various sizes. The bigger the better. Studies indicate that small-particle LDL raises a person's risk of having a heart attack by a factor of three, possibly because the diminutive particles are much more likely to work their way into the arterial wall. They are also thought to oxidize more readily than larger LDL particles. This tendency magnifies their plaque-forming potential. Small HDL particles are much less effective at soaking up their bad brethren. But having small LDL (so-called pattern B) is by far the worse condition.
"Everybody agrees that patients with a preponderance of small LDL particles are at significantly greater risk for heart disease," says Dr. K. Lance Gould, a cardiologist at the University of Texas Medical School in Houston. "The difference of opinion is how aggressive we should be in testing for it and treating it." Gould advocates testing everyone who has at least one cardiac risk factor (for risk factors, go to www.americanheart.org/presenter.jhtml?identifier=4726). The test, called subfraction analysis, costs around $100 and is usually not covered by insurance unless a person already has heart disease.
The American Heart Assn. (AHA) has no official guidelines for testing cholesterol particle size. "There isn't sufficient evidence yet to prove it's a better indicator" of cardiac risk than current measures, says Dr. Nieca Goldberg, an AHA spokesperson. In treating her own patients at Lenox Hill Hospital in New York, however, Goldberg says she tests for particle size in patients who already have heart disease but have a normal cholesterol profile or those who are at high risk for heart disease but have borderline LDL. Many doctors don't use the test, either because they don't know about it or because they prefer to make an inference from triglyceride levels. Some studies indicate that high tryglicerides might be an indicator of small LDLs.
The size of your LDL particles can determine how you're treated. If you have pattern B particles, you'll want to get your percentage LDL down to around 70 milligrams per deciliter, which is substantially lower than the optimal 100 mg/dL that the AHA advises. While statin drugs such as Lipitor can reduce the amount of LDL in your blood, they have little or no impact on the size of the molecules. Therefore, doctors also advise taking hefty doses of vitamin B3, or niacin, or drugs known as fibrates to increase both LDL and HDL particle size.
While reducing the amount of fat in your diet is important, people with small-particle LDL shouldn't go too low. Studies indicate your condition is likely to worsen if you get less than 25% of your calories from fat. Exercise, on the other hand, will help, with the greatest gains coming in proportion to the amount rather than the intensity of activity you do. When it comes to cholesterol, a long walk beats a short run.
By Kate Murphy