The amount of 'good' cholesterol in the blood is an important marker for heart disease, irrespective of how much the level of 'bad' cholesterol is lowered.
There are two types of cholesterol in the body: bad or low-density lipoprotein (LDL) cholesterol, and good or high-density lipoprotein (HDL) cholesterol. LDL carries cholesterol around the body in the bloodstream and dumps it in arteries, where it can cause narrowing and even blockage. It is this process that contributes to the development of diseases of the cardiovascular system. For example, when the arteries supplying blood to the heart become blocked, the result is a heart attack. On the other hand, HDL cholesterol is termed good because it clears cholesterol and takes it to the liver to be broken down. For this reason, it is not just the total cholesterol level that is significant (LDL+HDL), but also the ratio of HDL to the total. A high proportion of HDL to the total figure is preferable. However, it has not been clear whether a low HDL cholesterol level would remain a significant risk factor in people whose LDL cholesterol was reduced to very low levels.
Researchers from the Heart Research Institute in Sydney assessed the predictive value of HDL cholesterol levels in 9770 patients taking cholesterol-lowering drugs called statins. It was found that the higher the HDL or good cholesterol levels, the less likely they were to have a heart attack or any other cardiovascular event. Another finding was that having a low HDL could still be associated with a substantial increase in risk.
The results suggest that a low HDL should not be ignored even while patients are treated with statins. Lowering levels of bad cholesterol aggressively probably reduces the risk of heart disease and stroke by 40–50 per cent, but having a drug to raise HDL levels would likely cut the remaining risk by half. But raising HDL levels is difficult. One drug that does it, Niacin, has bothersome side effects. Further research is warranted to design drugs that can raise HDL cholesterol levels. At the moment, the only alternative for such patients is to become lean and become very active.