When the Framingham Heart Study was launched in 1948, little was known about the risk factors that contributed to heart attacks and strokes. In the intervening decades, the 5,000 original participants in this landmark study, along with their descendants, have taught scientists a great deal about the behavioral and physiologic determinants of cardiovascular disease, or CVD. Smoking, high blood pressure, diabetes, obesity, physical inactivity and high cholesterol have been identified as major contributors to CVD.
Cholesterol: Good or Bad?
Among the discoveries that emerged from the Framingham data is the distinction among various forms of cholesterol -- specifically, the types of cholesterol-carrying molecules, or lipoproteins, that transport cholesterol through your bloodstream. Low-density lipoproteins, or LDL, are molecules that deposit cholesterol along the inner walls of your arteries and contribute to the formation of plaque. High-density lipoproteins, or HDL, remove cholesterol from your arteries and transport it to your liver for metabolism. Total cholesterol measures all of the cholesterol in LDL, HDL and other cholesterol-bearing lipoproteins. LDL and HDL are popularly known as "bad" cholesterol and "good" cholesterol, respectively.
Evolving Cholesterol Standards
When medical experts first learned that a high cholesterol level increased a person's risk for heart disease, they established guidelines they hoped would reduce Americans' risk for developing atherosclerosis, or hardening of the arteries. The National Cholesterol Education Program, using information gathered from subsequent studies called Adult Treatment Panels, modified those initial cholesterol guidelines to conform to an evolving understanding of CVD and its causes.
Risk Levels
According to the American Heart Association, your total cholesterol level should be below 200, if you are otherwise healthy. Levels of 200 to 239 are "borderline high" and increase your risks for heart disease to a moderate degree. If your total cholesterol level is above 240, your risk for a heart attack is more than twice that of a person whose cholesterol is below 200. Fasting blood tests are the best way to check your cholesterol level, but total cholesterol and HDL levels from a non-fasting sample are usually fairy accurate.
Considerations
According to the Cleveland Clinic, your total cholesterol level is only one risk factor for CVD. If you do not have heart disease or if you don't have any risk factors for CVD, your HDL should be above 45, your LDL should be below 130 and your triglycerides should be less than 150. If you smoke, have a family history of heart disease, have high blood pressure, are overweight or have diabetes, your risk for CVD increases substantially. If you have any risk factors for cardiovascular disease, talk to your physician about what you can do to decrease your chances of a heart attack or stroke.
References
- Framingham Heart Study: The History of the Framingham Heart Study
- National Cholesterol Education Program: Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults
- American Heart Association: Cholesterol Levels
- Cleveland Clinic: Cholesterol Guidelines
