Low-density lipoproteins, or LDL, more commonly known as "bad cholesterol," are aggregates of proteins and lipids that allow for the transport of cholesterols and triglycerides within the bloodstream. While the cholesterol derived from these compounds is important for many fundamental functions -- synthesis of cell membranes, steroid hormones, vitamin D and bile acids -- over-accumulation of LDL particles constitutes an independent risk factor for coronary artery disease, or CAD, as well as peripheral vascular and cerebrovascular diseases. For this reason, the American Heart Association established the National Cholesterol Education Program III, or NCEP III, guidelines in 2001 to set goals for optimal LDL levels. It is important the note that different targets exist for individuals at varying levels of risk for vascular disease.
Low Risk
The NCEP III guidelines suggest that low-risk individuals maintain an LDL level of less than160 mg/dL. Low-risk individuals are those who have 0 to 1 risk factors for the development of CAD. Major risk factors, excluding elevated LDL cholesterol, include: cigarette smoking; blood pressure equal to or greater than 140/90 mm/Hg or current treatment with anti-hypertensive medications; family history of CAD in male first-degree relatives who are less than 55 or in female first-degree relatives who are less than 65; and an age of 45 or older among men and 55 or older among women. A more thorough estimate of risk can be assessed using the Framingham Cardiac Risk Calculator. In general, individuals in this category have a 10-year CAD risk of less than 10 percent.
Moderate Risk
The target LDL level for individuals at moderate risk is less than 130 mg/dL. Compared to those at low risk, these individuals have two or more risk factors and have a 10-year CAD risk of 10 to 20 percent. As these individuals are at a slightly higher risk for CAD, their target levels are lower, to reduce the risk of long-term CAD.
High Risk
The NCEP III guidelines state that the optimal level of LDL among individuals at high risk for CAD is less than 100 mg/dL. This target level is ideal for individuals with existing CAD or CAD risk equivalents, which include: atherosclerotic diseases, such as abdominal aortic aneurysm, peripheral vascular disease or carotid artery disease; diabetes; or a greater than 20 percent 10-year risk of having CAD, as determined by the Framingham Cardiac Risk Calculator. Recent studies have suggested that a more stringent LDL goal of less than 70 mg/dL is a reasonable clinical target to further prevent the risk for developing CAD, according to a 2004 article in the journal "Circulation."
Use of the Guidelines
These targets have been established by the NCEP to guide individuals and their physicians in determining optimal LDL levels based on risk factors as well as therapeutic goals. While these guidelines are recommendations, individuals should consult their physician for individualized management plans.
References
- American Heart Association: Good vs. Bad Cholesterol
- "Harper's Illustrated Biochemistry;" RK Murray, et al.; 2009
- National Heart, Lung, and Blood Instiute; Detection, Evaluation and Treatment of High Blood Cholesterol in Adults: Adult Treatment Panel III; National Cholesterol Education Program Expert Panel; May 2001
- "Circulation"; Implications of recent clinical trials for the National Cholesterol Education Program Adult Treatment Panel III guidelines; SM Grundy, et al.; 2004
