The “Good Cholesterol” Guide: What Does HDL Really Mean for your Heart?

In the mid-80s during my training at the University of Cincinnati Medical Center, a landmark clinical trial reported that reducing high levels of low-density lipoprotein (LDL) or “bad” cholesterol directly lowered the risk of heart disease in people who were otherwise healthy.

What was especially interesting to me was that most of my patients admitted to our Coronary Care Unit with heart disease did not have high levels of the “bad” LDL cholesterol, but rather low levels of HDL, the “good” cholesterol.   After leaving Cincinnati to do advanced medical training at Johns Hopkins, the first National Cholesterol Guidelines were released.  These guidelines were puzzling because they did not recommend testing for HDL cholesterol if total cholesterol levels were in the desirable range (less than 200 mg/dL).  I discussed this concern with my mentors Drs. Peter Kwiterovich and Tom Pearson and they agreed that it would be worth determining the extent to low HDL cholesterol occurred in the setting of heart disease and normal or “desirable” total cholesterol.

Using Dr. Pearson’s database of 1,000 who had undergone coronary arteriography at Johns Hopkins, we found to our surprise and interest, that low HDL was the most common cholesterol abnormality in men and women with heart disease and normal cholesterol.  Our follow-up study established that having a low HDL also predicted future cardiovascular (e.g., heart attack) events in this subgroup.  

If average levels of HDL-C are 40-50 mg/dL in men and 50-60 mg/dL in women, how concerned should we be if levels are outside this range?   We examined this question using data from The Framingham Offspring Study and found that low HDL is most problematic when it is associated with other risk factors such as high blood pressure, diabetes and cigarette smoking.  However, an “isolated” low HDL cholesterol level in otherwise healthy men and women does not make a significant contribution with respect to risk of heart disease. Conversely, a “high” HDL (greater than 60 mg/dL) is only protective when there are no other risk factors present.  

Bottom Line: Levels of HDL cholesterol serve as a good barometer of heart disease risk. Importantly, if levels are low but everything else is normal, there is little cause for concern.  However, when accompanied by high blood pressure, high blood glucose, excess weight and so forth, the focus should be to improve these factors in order to reduce your overall risk of heart disease.

Michael MIller, MD is a preventive cardiologist and author of “Heal Your Heart: The Positive Emotions Prescription to Prevent & Reverse Heart Disease”, published by Penguin Random House.