B vitamins in stroke prevention: time to reconsider

Area of Science:

• Neurology
• Nephrology
• Cardiovascular Medicine

Background:

• B vitamin therapy effectively lowers homocysteine levels, a potential factor in stroke.
• Cyanocobalamin (a form of vitamin B12) may negatively impact renal function and cardiovascular health in patients with kidney impairment.
• Previous stroke prevention trials with B vitamins yielded inconclusive results, possibly due to confounding effects of renal function.

Purpose of the Study:

• To investigate the efficacy of B vitamin therapy for stroke prevention based on renal function.
• To determine if cyanocobalamin's potential harm in renal impairment explains previous trial outcomes.
• To explore the differential effects of B vitamins on stroke risk in patients with normal versus impaired renal function.

Main Methods:

• Meta-analysis of individual patient data from two large randomized controlled trials (VISP and VITATOPS).
• Analysis stratified by renal function status (normal vs. impaired).
• Assessment of stroke risk in participants receiving B vitamin therapy, with specific attention to cyanocobalamin exposure.

Main Results:

• B vitamin therapy showed no benefit for stroke prevention in patients with impaired renal function exposed to high-dose cyanocobalamin (risk ratio 1.04, 95% CI 0.84-1.27).
• Patients with normal renal function not exposed to high-dose cyanocobalamin experienced significant stroke risk reduction with B vitamin therapy (0.78, 0.67-0.90).
• A significant interaction between renal function and B vitamin therapy efficacy was observed (p=0.03).

Conclusions:

• High-dose cyanocobalamin in B vitamin therapy is not beneficial and potentially harmful for stroke prevention in individuals with impaired renal function.
• B vitamin therapy, excluding cyanocobalamin, may be beneficial for stroke prevention in individuals with normal renal function.
• Further research into alternative B vitamins like folic acid, methylcobalamin, or hydroxycobalamin for homocysteine reduction and stroke prevention is warranted.