Lower Cholesterol, Lower Mortality . . .

Introduction

If your blood lipids - especially your low-density lipoprotein (LDL) cholesterol - are raised, your doctor will be trying to get you to lower them. After all, a clear link between raised blood lipids and earlier death from cardiovascular causes has been recognized for the last 50 years. There are different ways of lowering blood lipid levels, and researchers in Basel, Switzerland, have reviewed which ones may be more successful than others in reducing mortality. Their findings are published in the Archives of Internal Medicine, and we summarize them here.

What they did

The methods of lipid lowering that were considered were the statin drugs (HMGCo-A reductase inhibitors), fibrates, resins, niacin (vitamin B3), n-3 fatty acids (omega-3 fatty acids), and diets. Published studies were analyzed if they compared any of these lipid-lowering interventions with placebo (dummy tablets or usual diet), had a 6-month follow-up, and reported death rates.

Ninety-seven studies were analyzed, covering roughly 135,000 patients in treated groups and 135,000 in control groups. Analyses were limited to treatments in which there were at least 1000 patients in each group.

There were two major classes of trials: those regarded as 'primary prevention' of coronary heart disease (CHD), in which fewer than 10% of the participants actually had CHD, and 'secondary prevention', in which all the participants had CHD and the intent was to prevent a severe cardiac event.

The important measures for the analyses were the percentage cholesterol reduction, overall mortality, and cardiac mortality (i.e. death from Heart attack, sudden death, or heart failure).

The analyses resulted in calculations of the average risk ratio of the important measurements, along with estimation of the numbers needed to treat (NNT) per year to prevent one death.

What they found

For the statins (35 trials), the risk ratio for overall mortality was 0.87. In other words, for every 100 deaths in placebo-treated patients there would be 87 deaths in statin-treated patients. Fortunately, the mortality rate in these patients was not particularly high. This meant that 248 patients in a secondary prevention study (i.e. they all had CHD) or 855 patients in a primary prevention study would need to be treated to prevent one death. Risk ratios for cardiac mortality were also reduced with statins.

For fibrates (17 studies) the risk ratio for overall mortality was 1.0; i.e. there was no benefit of the drug on overall mortality. However, it was found there was a clear benefit on cardiac mortality, which was countered by an increase in the risk ratio for non-cardiac mortality, to 1.13. The side effects of fibrates can be serious, and presumably account for this effect.