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Vitamin Intervention For Stroke Prevention trial: an efficacy analysis
J David Spence1, Heejung Bang, Lloyd E Chambless
1The Stroke Prevention and Atherosclerosis Research Centre, Robarts Research Institute, London, Ontario, Canada. dspence@robarts.ca
Stroke
|October 22, 2005
Summary
Higher vitamin B12 doses may benefit patients with recurrent vascular events, especially those without malabsorption or renal issues. This targeted approach shows potential for improved outcomes in stroke prevention.
Area of Science:
- Cardiovascular Medicine
- Neurology
- Nutritional Science
Background:
- The Vitamin Intervention for Stroke Prevention (VISP) trial found no overall efficacy for combined vitamin therapy in preventing recurrent vascular events in non-disabling stroke patients.
- Potential reasons for VISP's lack of efficacy include widespread folate fortification, B12 dosing strategies, and patient factors like malabsorption or renal impairment.
- Newer evidence suggests a re-evaluation of vitamin therapy efficacy in specific patient subgroups.
Purpose of the Study:
- To re-analyze the VISP trial data focusing on a subgroup of patients most likely to benefit from vitamin therapy.
- To investigate the efficacy of higher-dose vitamin B12 in preventing vascular events in a selected patient population.
Main Methods:
- Excluded patients with very low or very high baseline vitamin B12 levels (<250 and >637 pmol/L) to minimize effects of malabsorption or external supplementation.
- Excluded patients with significant renal impairment (glomerular filtration rate <46.18 mL/min/1.73 m²).
- Conducted an efficacy analysis on the remaining 2155 patients based on predefined subgroup criteria.
Main Results:
- In the selected subgroup, the high-dose vitamin group showed a 21% reduction in the combined endpoint of ischemic stroke, coronary disease, or death compared to the low-dose group (P=0.049, adjusted P=0.056).
- Kaplan-Meier analysis indicated that patients with median or higher baseline B12 levels randomized to high-dose vitamins had the best outcomes.
- Conversely, patients with below-median B12 levels assigned to low-dose vitamins experienced the worst outcomes (P=0.02 for stroke, death, and coronary events).
Conclusions:
- Vitamin B12 plays a critical role in managing total homocysteine levels, particularly in the context of widespread folate fortification.
- Higher doses of vitamin B12 and potentially other homocysteine-lowering strategies may be necessary for certain patient populations to achieve therapeutic benefits.
- These findings support a more personalized approach to vitamin therapy for vascular event prevention.