Number-needed-to-treat analysis of the prevention of myocardial infarction and death by antidyslipidemic therapy.

BACKGROUND Atherosclerosis of the coronary arteries is the most common cause of death in the United States for persons over the age of 45. Dyslipidemia is one of the risk factors for the development of coronary atherosclerosis. Recent studies suggest that treating dyslipidemia in persons with coronary atherosclerosis may decrease morbidity and mortality. METHODS A meta-analysis of 33 studies on the clinical and angiographic benefits of treating dyslipidemia in the prevention of morbidity and mortality from cardiovascular disease was performed. These benefits are quantitated in the form of "number needed to treat" (NNT) as an estimate of the public health benefit. The NNT is defined as the number of people that need to be treated to prevent one event. RESULTS Treatment of dyslipidemia in persons with multiple atherosclerosis risk factors alone, ie, primary prevention, was effective in preventing myocardial infarction and all-cause death. In six trials of primary prevention, excluding the British cooperative trial using clofibrate, the NNT was 53 to prevent a nonfatal MI and 190 to prevent all-cause death (4.8 years treatment with total cholesterol reduction of 15%). Treatment of dyslipidemia in people with known atherosclerosis, ie, secondary and tertiary prevention, was also effective in preventing myocardial infarctions and death from all causes. For 23 trials of secondary and tertiary prevention, the NNT was 37 to prevent death from any cause (4.9 years treatment with total cholesterol reduction of 18%). In the trials with quantitative angiography, the NNT was 7 to prevent progression of coronary atherosclerosis and 10 to induce regression of coronary atherosclerosis (2.5 years treatment with a low-density lipoprotein cholesterol reduction of 28%). Similar benefits were observed in those trials employing HMG CoA reductase inhibitors. Benefits may be similar with niacin or dietary therapy, but these therapies did not reach significance in all categories of benefits, potentially due to beta error. These treatment benefits are comparable to other secondary prevention measures such as aspirin or beta blockers. The benefits appeared to extend to persons over 65, with less clearly defined benefits for women. CONCLUSIONS These results support the overall clinical benefit of treating dyslipidemia, both in persons with and without known atherosclerosis.