Combined analyses and extended follow-up of two randomized controlled homocysteine-lowering B-vitamin trials

Authors


Marta Ebbing, MD, Department of Heart Disease, Haukeland University Hospital, Jonas Liesvei 65, Bergen, Norway 5021. (Tel: +47 55972196; Fax: +47 55975144; e-mail: marta.ebbing@helse-bergen.no).

Abstract

Abstract.  Ebbing M., Bønaa K.H., Arnesen E., Ueland P.M., Nordrehaug J.E., Rasmussen K., Njølstad I., Nilsen D.W., Refsum H., Tverdal A., Vollset S.E., Schirmer H., Bleie Ø., Steigen T., Midttun Ø., Fredriksen Å., Pedersen E.R., Nygård O. (From the Departments of 1Heart Disease, Haukeland University Hospital, Bergen; Heart Disease, University Hospital of North Norway; Department of Community Medicine, University of Tromsø, Tromsø; Institute of Medicine, University of Bergen, Bergen; Department of Clinical Medicine, University of Tromsø, Tromsø; Department of Cardiology, Stavanger University Hospital, Stavanger; Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK; Division of Epidemiology, the Norwegian Institute of Public Health, Oslo; Department of Public Health and Primary Health Care, University of Bergen; Bevital AS, Bergen; Norway) Combined Analyses and Extended Follow-Up of Two Randomized Controlled Homocysteine-Lowering B-Vitamin Trials. J Intern Med 2010; 268: 367–382.

Objectives.  In the Norwegian Vitamin Trial and the Western Norway B Vitamin Intervention Trial, patients were randomly assigned to homocysteine-lowering B-vitamins or no such treatment. We investigated their effects on cardiovascular outcomes in the trial populations combined, during the trials and during an extended follow-up, and performed exploratory analyses to determine the usefulness of homocysteine as a predictor of cardiovascular outcomes.

Design.  Pooling of data from two randomized controlled trials (1998–2005) with extended post-trial observational follow-up until 1 January 2008.

Setting.  Thirty-six hospitals in Norway.

Subjects.  6837 patients with ischaemic heart disease.

Interventions.  One capsule per day containing folic acid (0.8 mg) plus vitamin B12 (0.4 mg) and vitamin B6 (40 mg), or folic acid plus vitamin B12, or vitamin B6 alone or placebo.

Main outcome measures.  Major adverse cardiovascular events (MACEs; cardiovascular death, acute myocardial infarction or stroke) during the trials and cardiovascular mortality during the extended follow-up.

Results.  Folic acid plus vitamin B12 treatment lowered homocysteine levels by 25% but did not influence MACE incidence (hazard ratio, 1.07; 95% CI, 0.95–1.21) during 39 months of follow-up, or cardiovascular mortality (hazard ratio, 1.12; 95% CI, 0.95–1.31) during 78 months of follow-up, when compared to no such treatment. Baseline homocysteine level was not independently associated with study outcomes. However, homocysteine concentration measured after 1–2 months of folic acid plus vitamin B12 treatment was a strong predictor of MACEs.

Conclusion.  We found no short- or long-term benefit of folic acid plus vitamin B12 on cardiovascular outcomes in patients with ischaemic heart disease. Our data suggest that cardiovascular risk prediction by plasma total homocysteine concentration may be confined to the homocysteine fraction that does not respond to B-vitamins.

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