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Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials.

Abstract

OBJECTIVE

To evaluate the effect of vitamin E supplementation on incident total, ischaemic, and haemorrhagic stroke.

DESIGN

Systematic review and meta-analysis of randomised, placebo controlled trials published until January 2010.

DATA SOURCES

Electronic databases (Medline, Embase, Cochrane Central Register of Controlled Trials) and reference lists of trial reports. Selection criteria Randomised, placebo controlled trials with ≥1 year of follow-up investigating the effect of vitamin E on stroke. Review methods and data extraction Two investigators independently assessed eligibility of identified trials. Disagreements were resolved by consensus. Two different investigators independently extracted data. Risk ratios (and 95% confidence intervals) were calculated for each trial based on the number of cases and non-cases randomised to vitamin E or placebo. Pooled effect estimates were then calculated.

RESULTS

Nine trials investigating the effect of vitamin E on incident stroke were included, totalling 118 765 participants (59 357 randomised to vitamin E and 59 408 to placebo). Among those, seven trials reported data for total stroke and five trials each for haemorrhagic and ischaemic stroke. Vitamin E had no effect on the risk for total stroke (pooled relative risk 0.98 (95% confidence interval 0.91 to 1.05), P=0.53). In contrast, the risk for haemorrhagic stroke was increased (pooled relative risk 1.22 (1.00 to 1.48), P=0.045), while the risk of ischaemic stroke was reduced (pooled relative risk 0.90 (0.82 to 0.99), P=0.02). There was little evidence for heterogeneity among studies. Meta-regression did not identify blinding strategy, vitamin E dose, or morbidity status of participants as sources of heterogeneity. In terms of absolute risk, this translates into one additional haemorrhagic stroke for every 1250 individuals taking vitamin E, in contrast to one ischaemic stroke prevented per 476 individuals taking vitamin E.

CONCLUSION

In this meta-analysis, vitamin E increased the risk for haemorrhagic stroke by 22% and reduced the risk of ischaemic stroke by 10%. This differential risk pattern is obscured when looking at total stroke. Given the relatively small risk reduction of ischaemic stroke and the generally more severe outcome of haemorrhagic stroke, indiscriminate widespread use of vitamin E should be cautioned against.

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  • Authors+Show Affiliations

    ,

    Division of Preventive Medicine, Department of Medicine; Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215-1204, USA. mschuerks@rics.bwh.harvard.edu

    , , ,

    Source

    BMJ (Clinical research ed.) 341: 2010 Nov 04 pg c5702

    MeSH

    Adult
    Aged
    Brain Ischemia
    Dietary Supplements
    Humans
    Intracranial Hemorrhages
    Middle Aged
    Randomized Controlled Trials as Topic
    Risk Factors
    Stroke
    Vitamin E
    Vitamins

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    21051774

    Citation

    Schürks, Markus, et al. "Effects of Vitamin E On Stroke Subtypes: Meta-analysis of Randomised Controlled Trials." BMJ (Clinical Research Ed.), vol. 341, 2010, p. c5702.
    Schürks M, Glynn RJ, Rist PM, et al. Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. BMJ. 2010;341:c5702.
    Schürks, M., Glynn, R. J., Rist, P. M., Tzourio, C., & Kurth, T. (2010). Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. BMJ (Clinical Research Ed.), 341, p. c5702. doi:10.1136/bmj.c5702.
    Schürks M, et al. Effects of Vitamin E On Stroke Subtypes: Meta-analysis of Randomised Controlled Trials. BMJ. 2010 Nov 4;341:c5702. PubMed PMID: 21051774.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. AU - Schürks,Markus, AU - Glynn,Robert J, AU - Rist,Pamela M, AU - Tzourio,Christophe, AU - Kurth,Tobias, Y1 - 2010/11/04/ PY - 2010/11/6/entrez PY - 2010/11/6/pubmed PY - 2010/11/17/medline SP - c5702 EP - c5702 JF - BMJ (Clinical research ed.) JO - BMJ VL - 341 N2 - OBJECTIVE: To evaluate the effect of vitamin E supplementation on incident total, ischaemic, and haemorrhagic stroke. DESIGN: Systematic review and meta-analysis of randomised, placebo controlled trials published until January 2010. DATA SOURCES: Electronic databases (Medline, Embase, Cochrane Central Register of Controlled Trials) and reference lists of trial reports. Selection criteria Randomised, placebo controlled trials with ≥1 year of follow-up investigating the effect of vitamin E on stroke. Review methods and data extraction Two investigators independently assessed eligibility of identified trials. Disagreements were resolved by consensus. Two different investigators independently extracted data. Risk ratios (and 95% confidence intervals) were calculated for each trial based on the number of cases and non-cases randomised to vitamin E or placebo. Pooled effect estimates were then calculated. RESULTS: Nine trials investigating the effect of vitamin E on incident stroke were included, totalling 118 765 participants (59 357 randomised to vitamin E and 59 408 to placebo). Among those, seven trials reported data for total stroke and five trials each for haemorrhagic and ischaemic stroke. Vitamin E had no effect on the risk for total stroke (pooled relative risk 0.98 (95% confidence interval 0.91 to 1.05), P=0.53). In contrast, the risk for haemorrhagic stroke was increased (pooled relative risk 1.22 (1.00 to 1.48), P=0.045), while the risk of ischaemic stroke was reduced (pooled relative risk 0.90 (0.82 to 0.99), P=0.02). There was little evidence for heterogeneity among studies. Meta-regression did not identify blinding strategy, vitamin E dose, or morbidity status of participants as sources of heterogeneity. In terms of absolute risk, this translates into one additional haemorrhagic stroke for every 1250 individuals taking vitamin E, in contrast to one ischaemic stroke prevented per 476 individuals taking vitamin E. CONCLUSION: In this meta-analysis, vitamin E increased the risk for haemorrhagic stroke by 22% and reduced the risk of ischaemic stroke by 10%. This differential risk pattern is obscured when looking at total stroke. Given the relatively small risk reduction of ischaemic stroke and the generally more severe outcome of haemorrhagic stroke, indiscriminate widespread use of vitamin E should be cautioned against. SN - 1756-1833 UR - https://www.unboundmedicine.com/medline/citation/21051774/full_citation L2 - http://www.bmj.com/cgi/pmidlookup?view=long&pmid=21051774 DB - PRIME DP - Unbound Medicine ER -