Fish oil not associated with cardiovascular benefits

Patients with cardiovascular risk factors who took n-3 polyunsaturated fatty acids daily appeared to have no reduction in cardiovascular mortality or morbidity, according to a new study.

Researchers in Italy performed a double-blind, placebo-controlled clinical trial that randomly assigned general-practice patients with atherosclerotic vascular disease or more than one cardiovascular risk factor but no myocardial infarction to receive 1 g of n-3 fatty acids daily or olive oil as a placebo. The goal of the study was to determine the potential benefit of n-3 fatty acids in this patient subgroup.

The initial primary end point was cumulative death, nonfatal myocardial infarction and nonfatal stroke, but because of a lower-than-anticipated event rate, it was revised at one year to be time to death or hospital admission related to cardiovascular causes. Secondary end points included the initial primary end point; a composite of time to death from cardiovascular causes, nonfatal myocardial infarction or nonfatal stroke; death due to coronary heart disease; and sudden death due to cardiac causes. The results were published in the May 9 New England Journal of Medicine.

Overall, 12,513 patients cared for by 860 general practitioners were enrolled in the study, and 12,505 were included in the intention-to-treat analysis. A total of 61.5% of the patients were men, and the mean patient age was 64 years. In the intention-to-treat analysis, 6,239 patients received n-3 fatty acids and 6,266 received placebo. At a median follow-up of five years, 1,478 patients (11.8%) had experienced the primary end point, 733 in the n-3 fatty acids group and 745 in the placebo group (11.7% vs. 11.9%; adjusted hazard ratio with n-3 fatty acids, 0.97; 95% CI, 0.88 to 1.08; P=0.58). Rates of all of the secondary end points were also similar between groups.

The authors concluded that in this study population, n-3 fatty acids had no effect on cardiovascular morbidity and mortality. They noted that their results differ from those of previous trials, which found a benefit mainly from reducing sudden deaths related to cardiac causes. "It is conceivable that the effects of n-3 fatty acids become manifest primarily in patients who are particularly prone to ventricular arrhythmic events (e.g., those with a myocardial scar or left ventricular dysfunction)," the authors wrote. They noted that research into the safety profile of n-3 fatty acids in the latter population could be useful.