GOOD CHOLESTEROL (HDL)

(July 2001)

The effects of raising blood levels of good cholesterol (HDL) on risk of heart attack.

Blood cholesterol levels are made up of two major components, the dangerous low-density lipoprotein cholesterol (LDL - bad cholesterol) and protective high-density lipoprotein cholesterol (HDL - good cholesterol).

It is well known that those with high HDL are at less risk of a heart attack. Some people who suffer non-fatal or fatal heart attacks have high cholesterol levels and high blood levels of LDL; others have normal LDL levels, but low blood concentrations of protective HDL. The persisting question is whether raising HDL levels by drug treatment will reduce the risk of heart attack. An article in The New England Journal of Medicine titled Gemfibrozil for the Secondary Prevention of Coronary Heart Disease in Men with Low Levels of High Density Lipoprotein Cholesterol provides useful information. The study is a collaborative venture of multiple Veterans Affairs Medical Centers. All the men had evidence of coronary artery disease; 1,264 were given the drug Gemfibrozil; 1,267 acted as controls.

Over a follow-up period of an average of five years, those who received Gemfibrozil increased their HDL levels by 6 percent and had a 22 to 23 percent reduction in heart attacks and deaths from coronary artery disease.

Commentary: This is not a great study. There are three problems:

Still, the study is a useful contribution, and the changes found are in the right direction.

for the very good evidence that a high HDL protects against heart attack and a low HDL increases the risk. That is why Healthful Life measures HDL every two years, along with total blood cholesterol levels. The results reported in this study make sense. Furthermore, since this study was published, additional impressive evidence has appeared on the protective effects of HDL in regard to coronary heart disease and heart attacks. An HDL blood level of less than 40 is too low. With HDL, the higher the better, so a blood level of 65 milligrams offers considerably more protection than 45 milligrams, though both are in the normal range. The problem is that it is not easy to raise HDL levels - exercise, stopping cigarette smoking, weight loss, and one or two drinks of wine a day (no more, please) may help somewhat, but usually will not increase levels by more than 5 to 15 percent. What we really need is drugs that can raise HDL levels by at least 20 to 30 percent. That would have a reasonably dramatic effect in reducing the risk of heart attack.

It is critical to know not only one’s total cholesterol (or the blood level of LDL - bad cholesterol), but also the ratio of cholesterol (or LDL) to HDL. If the cholesterol to HDL ratio is 4 or less, that indicates a lessened risk of heart attack. If it is greater than 6, the risk of heart attack is above average. Even if it is 5 or above, you should be paying attention and doing something about it, especially if you have other risk factor for heart attack (high blood pressure, smoking, diabetes, obesity, strong family history).

Rubins, H.B., et al. Gemfibrozil for the secondary prevention of coronary heart disease in men with low levels of high-density lipoprotein cholesterol. The New England Journal of Medicine. Vol 341. (August 5) Pgs 410-418. 1999.