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Plasma homocysteine as a cardiovascular risk factor: causal, consequential, or of no consequence?
1Department of Cardiovascular Medicine, James Connolly Memorial Hospital, Dublin, Ireland.
Insights
Elevated homocysteine levels may link to cardiovascular disease risk. However, recent studies question this association, highlighting the need for randomized trials to confirm the benefits of homocysteine-lowering therapy.
Area of Science:
- Cardiovascular Medicine
- Biochemistry
- Epidemiology
Background:
- Elevated plasma total homocysteine has been implicated as a potential causal factor in atherosclerotic cardiovascular diseases.
- Previous research suggested an independent association between homocysteine and cardiovascular disease (CVD) occurrence, progression, and recurrence, irrespective of traditional risk factors.
Purpose of the Study:
- To critically evaluate the relationship between elevated plasma total homocysteine and the incidence of cardiovascular disease.
- To assess the impact of study design, bias, and confounding factors on the observed association.
Main Methods:
- Review and analysis of existing cross-sectional, retrospective case-control, nested case-control, and prospective studies.
- Emphasis on the critical role of randomized controlled trials (RCTs) in establishing causality.
Main Results:
- A stronger association between homocysteine and CVD was generally observed in cross-sectional and retrospective studies compared to nested case-control or prospective designs.
- Recent data have introduced uncertainty regarding the reliability of the homocysteine-cardiovascular disease link.
Conclusions:
- Study design, bias, and confounding are crucial considerations in evaluating the homocysteine-cardiovascular disease relationship.
- Randomized controlled trials of homocysteine-lowering therapy, such as folic acid, are essential to definitively resolve this association.
- Pending trial outcomes, empirical prescription of homocysteine-lowering therapy may be considered for high-risk cardiovascular patients.
Abstract:
Elevated plasma total homocysteine may be causally related to the risk of atherosclerotic cardio-vascular diseases. Many significant studies indicate an effect by elevated homocysteine on cardiovascular disease occurrence, progression, and recurrence that is independent of traditional risk factors. However, recent data have cast doubt on the veracity of the relationship between elevated plasma total homocysteine and the incidence of cardiovascular disease. In general, a stronger relationship has been found in cross-sectional and retrospective case-control studies than in nested case-control or prospective studies. The issues of study design, bias, and confounding are critical to an analysis of this putative relationship, and their effects can only be avoided by randomized controlled trials of homocysteine-lowering therapy (folic acid). While awaiting the outcome of these trials, there may already be sufficient evidence to prescribe homocysteine-lowering therapy in subjects deemed to be at high risk of cardiovascular disease.