John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. In August 2017, we published the third update of the Cochrane Review of homocysteine-lowering interventions with B complex vitamins for preventing cardiovascular disease. The review investigates their impact on this common cause of death and we asked one of the authors, Mark Dayer from Taunton and Somerset NHS Trust in the UK, to bring us up to date in this podcast.

Mark: Cardiovascular disease, which includes coronary artery disease, stroke and peripheral vascular disease, kills millions of people worldwide each year and elevated levels of homocysteine in the body may be a risk factor for its development. To try to counter this, vitamin B6 (Pyridoxine), B9 (Folic Acid) and B12 (Cyanocobalamin) supplements, which have been shown to lower homocysteine levels, have been investigated as potential agents to reduce cardiovascular events. Therefore, we’ve been reviewing the randomised trials of these interventions for the past decade, to see their effects on myocardial infarction and stroke, in particular.
In this third update, we identified three new randomised trials, bringing us up to 15 trials involving more than 70,000 participants that had been published between 2002 and 2015. Overall, the quality of evidence from these studies was high, and it suggests that the impact of the homocysteine-lowering interventions on some cardiovascular events is no different to that from placebos. For example, across 12 trials, including nearly 47,000 people, 6.1% of those in the homocysteine-lowering group had a myocardial infarction compared to 6.0% in the placebo group. When we looked at death from any cause, there were 11 trials, with nearly 45,000 participants, and the rate of death from any cause was 12.4% in the homocysteine lowering group, versus 12.3% in the placebo group.
On the other hand, there was an effect on stroke. In 10 trials, with 44,000 participants, the relative risk was 0.90 with a 95% confidence interval of 0.82-0.99: 4.6% of those in the homocysteine-lowering group had a stroke compared to 5.1% in the placebo group.
In summary, the existing evidence from randomised trials shows no differences in effects of homocysteine-lowering interventions in the form of supplements of vitamins B6, B9 or B12 given alone or in combination compared with placebo on myocardial infarction, death from any cause or adverse events. In terms of stroke, there is a small difference in effect favouring homocysteine-lowering interventions. Looking to the future, there is a need for additional trials comparing homocysteine-lowering interventions combined with antihypertensive medication versus antihypertensive medication alone, and comparing high versus low dose homocysteine-lowering interventions.

John: If would like to find out more about the existing evidence and watch for the fourth update of the review if additional trials are done, you can find it in the Cochrane Library. Just go to Cochrane Library dot com and search 'homocysteine and stroke'.