Homocysteine-Lowering Therapy and Risk for Venous Thromboembolism
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BACKGROUND: Elevated total homocysteine levels are associated with a higher risk for venous thromboembolism. Whether decreasing homocysteine levels with vitamin therapy reduces the risk for venous thromboembolism is not known. OBJECTIVE: To determine whether decreasing homocysteine levels alters the risk for symptomatic venous thromboembolism. DESIGN: Secondary analysis of data from the randomized, placebo-controlled Heart Outcomes Prevention Evaluation 2 (HOPE-2) trial. SETTING: 145 clinical centers in 13 countries. PARTICIPANTS: 5522 persons 55 years of age or older with known cardiovascular disease or diabetes mellitus and at least 1 other risk factor for vascular disease. INTERVENTION: A daily supplement of 2.5 mg of folic acid, 50 mg of vitamin B(6), and 1 mg of vitamin B(12) or matching placebo for 5 years. MEASUREMENT: Prospectively diagnosed and confirmed symptomatic deep venous thrombosis or pulmonary embolism. RESULTS: The geometric mean homocysteine level decreased by 2.2 micromol/L in the vitamin therapy group and increased by 0.80 micromol/L in the placebo group. Venous thromboembolism occurred in 88 participants during a mean follow-up of 5 years. The incidence rate of venous thromboembolism was the same in the vitamin therapy group and the placebo group (0.35 per 100 person-years; hazard ratio, 1.01 [95% CI, 0.66 to 1.53]). Vitamin therapy did not reduce the risk for deep venous thrombosis (hazard ratio, 1.04 [CI, 0.63 to 1.72]), pulmonary embolism (hazard ratio, 1.14 [CI, 0.57 to 2.28]), or unprovoked venous thromboembolism (hazard ratio, 1.21 [CI, 0.66 to 2.23]). LIMITATIONS: The proportion of patients with a previous episode of venous thromboembolism at enrollment was not known, and venous thromboembolism events were not centrally adjudicated. CONCLUSION: Decreasing homocysteine levels with folic acid and vitamins B6 and B12 did not reduce the risk for symptomatic venous thromboembolism.
