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. 2017 Aug 17;2017(8):CD006612. doi: 10.1002/14651858.CD006612.pub5

Summary of findings 1. Homocysteine‐lowering interventions (Vitamin B6 (pyridoxine; pyridoxal); B9 (folic acid) or B12 (cyanocobalamin) compared with placebo or standard care for preventing cardiovascular events.

Homocysteine‐lowering interventions (vitamins B6 (pyridoxine; pyridoxal); B9 (folic acid) or B12 (cyanocobalamin) compared with placebo or standard care for preventing cardiovascular events
Patient or population: adults at risk of or with established cardiovascular disease
Settings: outpatients
Intervention: homocysteine‐lowering interventions (vitamins B6 (pyridoxine; pyridoxal), B9 (folic acid) or B12 (cyanocobalamin).
Comparison: placebo or standard care
Outcomes Illustrative comparative risks* (95% CI) Relative effect
(95% CI) No of Participants
(studies) Quality of the evidence
(GRADE) Comments
Assumed risk Corresponding risk
Placebo or standard care Homocysteine‐lowering interventions(vitamins B6 (pyridoxine; pyridoxal); B9 (folic acid) or B12 (cyanocobalamin)
Myocardial infarction
Follow‐up: 1 to 7.3 years 60 per 1000 61 per 1000
(57 to 66) RR 1.02 
(0.95 to 1.10) 46,699
(12 trials) ⊕⊕⊕⊕
high  
Stroke
Follow‐up: 1 to 7.3 years 51 per 1000 46 per 1000
(42 to 50) RR 0.90 
(0.82 to 0.99) 44,224
(10 trials) ⊕⊕⊕⊕
high  
Death by any cause
Follow‐up: 1 to 7.3 years 123 per 1000 124 per 1000
(118 to 130) RR 1.01 
(0.96 to 1.06) 44,817
(11 trials) ⊕⊕⊕⊕
high  
Adverse events
Follow‐up: 3.4 to 7.3 years 85 per 1000 91 per 1000
(85 to 97) RR 1.07 
(1.00 to 1.14) 35,788
(8 trials) ⊕⊕⊕⊕
high Cancer is the only reported adverse event.
*The basis for the assumed risk (e.g. the median control group risk across studies) is the outcomes of the study control arms. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; RR: Risk ratio;
GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.