Antioxidants May Not Reduce Risk of Cardiac Mortality

ANAHEIM, Calif.--Preliminary findings of the United Kingdom's (UK) Heart Protection Study indicated that while simvastatin lowered risk of death from coronary events and stroke, antioxidant vitamins did not. Rory Collins, BSc, co-director of the Clinical Trial Service Unit (CTSU) of the UK's Oxford University and lead researcher for the Heart Protection Study, presented these findings at the American Heart Association's (AHA) Nov. 13 meeting.

Previous research, reported in the August issue of Arteriosclerosis, Thrombosis and Vascular Biology (21: 1320-6, 2001) indicated that antioxidant vitamins and minerals may help statin drugs reduce overall cholesterol levels, but when used in combination, they may impede the drugs' ability to increase HDL cholesterol levels. In this 12-month study, 153 patients with coronary artery disease and low levels of HDL cholesterol were randomly assigned to four groups: 1) simvastatin with niacin; 2) vitamins C and E, beta-carotene and selenium; 3) combination of statins and antioxidants; or 4) placebo. Results indicated that statin and statin/antioxidant groups had significant reductions in plasma cholesterol, triglycerides and LDL cholesterol. However, HDL improved in the statin-only group, but not in the subjects taking antioxidants.

The Medical Research Council/British Heart Foundation Heart Protection Study was set up by Oxford University's CTSU to determine the long-term benefits of cholesterol-lowering drug therapy for particular patients and the benefits or risks of antioxidant vitamin supplementation. The Heart Protection Study is currently the world's largest trial of cholesterol-lowering therapy and antioxidant vitamins in patients who are at higher risk of death from coronary events because of previous diagnoses of coronary heart disease (CHD), occlusive arterial disease, diabetes or hypertension. The study involves 20,536 subjects from 69 U.K. hospitals who were enrolled between July 1994 to May 1997. Subjects were randomly placed in simvastatin (40 mg/d Zocor, provided by Merck & Co. Inc.) and placebo groups. Within these groups, half of the subjects were randomly assigned to receive vitamins E (600 mg/d), C (250 mg/d) and beta-carotene (20 mg/d) or placebo.

Oxford University's CTSU (www.ctsu.ox.ac.uk) reported that compliance with the study treatments has been good, resulting in large average reductions in blood levels of total cholesterol (1.3 mmol/L) and LDL cholesterol (1.0 mmol/L), and large increases in antioxidant vitamin levels. During the scheduled treatment period, approximately 4,500 major vascular events (2,000 coronary events and 1,000 strokes) and approximately 3,000 deaths (1,500 from vascular causes) were reported.

Collins' presentation at the AHA meeting focused mostly on the highly beneficial effects of simvastatin; however, small mention of antioxidants' role in heart health was also made. The comparison between simvastatin plus vitamins and vitamins alone did not yield any evidence that the antioxidants used could prevent deaths, heart attacks, strokes or other vascular disease outcomes in any of the groups. Collins noted that antioxidant vitamins did provide strong safety evidence.

"We found no excess risk of strokes due to bleeding or of cancers at any site," Collins said. "This contradicts the apparent adverse trends in some previous smaller studies of vitamin E and beta-carotene. We shall continue to follow the health of the study volunteers for years to come, so should know if some benefit emerges later."

Study funding (approximately $32 million) was provided by the U.K.'s Medical Research Council, BHF, Merck & Co. Inc. and Roche Vitamins Ltd. More information on this study can be obtained at the British Heart Foundation's Web site (www.bhf.org.uk).