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Homocysteine, hypertension and stroke
1Department of Epidemiology & Public Health, University College Cork, Republic of Ireland.
Insights
Elevated homocysteine levels are linked to higher risks of stroke and carotid artery disease, but more prospective research is needed to confirm causality and understand influencing factors. Further studies are essential to clarify the homocysteine-stroke relationship and its public health implications.
Area of Science:
- Cardiovascular epidemiology
- Nutritional biochemistry
- Genetics
Background:
- Observational studies suggest elevated homocysteine is associated with increased risk of carotid artery disease and stroke.
- Concerns exist regarding confounding factors like renal impairment, diet, and smoking in hyperhomocysteinemia.
- The link between hyperhomocysteinemia and hypertension is limited and inconsistent.
Purpose of the Study:
- To highlight the need for prospective studies on homocysteine and vascular disease.
- To emphasize the requirement for research on confounding factors and interactions with other risk factors.
- To call for studies investigating the homocysteine-hypertension relationship.
Main Methods:
- Review of existing observational and genetic studies.
- Identification of gaps in current research, particularly prospective studies.
- Call for studies with robust data on confounders and precise homocysteine measurements.
Main Results:
- Current evidence is largely observational, with a paucity of prospective studies.
- Genetic factors like MTHFR polymorphism are not consistently linked to stroke.
- Inconsistent evidence exists for the association between homocysteine and hypertension.
Conclusions:
- Additional prospective studies are needed to establish a causal link between homocysteine and vascular disease, including stroke and hypertension.
- Understanding the homocysteine-stroke relationship requires characterizing the association's form (linear vs. threshold) and interactions with risk factors.
- Randomized controlled trials of homocysteine-lowering interventions are ultimately necessary to confirm a causal role.
Abstract:
The balance of evidence from observational studies suggests that elevated homocysteine levels are associated with increased risk of carotid artery disease and stroke. There is however a paucity of prospective studies. There are also concerns regarding confounding due to factors associated with hyperhomocysteinemia, including renal impairment, an atherogenic diet and cigarette smoking. Homozygosity for a defective thermolabile variant of MTHFR, a common genetic polymorphism which results in hyperhomocysteinemia, has not been consistently linked with stroke or other vascular disease. There is a need for additional prospective studies with data on relevant confounders, sufficient power to characterise the form of the association between homocysteine concentrations and stroke risk, whether linear or threshold, and power to study interactions between homocysteine, other dietary markers and established stroke risk factors such as smoking and hypertension. Similarly, the evidence linking hyperhomocysteinemia with hypertension is limited and inconsistent. Given the biological mechanisms proposed in support of the homocysteine-CVD hypothesis, one would predict a positive association between homocysteine and blood pressure. There is a need to address this hypothesis directly in studies with reliable measurements of both homocysteine and blood pressure. Ultimately, the case for a causal role for elevated homocysteine levels in vascular disease, including hypertension and stroke, will depend on data from randomised controlled trials of homocysteine lowering interventions. Given the high prevalence of hyperhomocysteinemia in apparently well nourished populations and the tendency for homocysteine concentrations to increase with age, modest effects of homocysteine on stroke risk will have profound implications for public health.