title: [Meta-analysis on effect of combined supplementation of folic acid, vitamin B12 and B6 on risk of cardio-cerebrovascular diseases in randomized control trials].
abstract: OBJECTIVE
  To evaluate the effect of the combined supplementation of folic acid, vitamin B12 and B6 on the risk of cardio-cerebrovascular diseases.
  
  
  METHODS
  The literatures of randomized control trials about the relationship between the combined supplementation of folic acid, vitamin B12 and B6 and risk of cardio-cerebrovascular diseases from 1980 to 2014 were retrieved, and the eligible studies were screened for a Meta-analysis. The study indicators were the incidences of cardiovascular disease events, myocardial infarction and stroke. The cffect indicators were relative risk(RR)and 95% confidence interval(CI). Jadad score was used for the quality evaluation of the trials used in the study.
  
  
  RESULTS
  The literatures of 11 randomized control trials, involving 26 395 patients, were used in the Meta-analysis. The combined supplementation of B vitamins had no effect on the incidence of cardiovascular disease events(RR=1.00, 95% CI: 0.94-1.07)based on 8 studies. The combined supplementation of B vitamins had no effect on the incidence of myocardial infarction(RR= 1.03, 95% CI: 0.94-1.13)based on 9 studies. The combined supplementation of B vitamins could reduce the incidence of stroke by 14%(RR=0.86, 95%CI: 0.78-0.95)based on 9 studies. Compared with the control group, Taking folic acid combined with vitamin B12 and B6 could reduce the level of homocysteine by 2.53 μmol/L(95%CI:-3.93--1.12). Subgroup analysis indicated that the follow-up time, the dosage of folic acid and vitamin B12 and B6, the history of diseases had no confounding effect on the incidence of cardio-cerebrovascular disease events. But the subgroup analysis for stroke showed that with the extension of follow-up time, the supplementation of B vitamins could reduce the risk of stroke. The effect of folic acid and B12 in small dosage seemed more significant in the prevention of stroke, while the preventive effect of B6 increased with increasing dosage. The preventive effect of combined supplementation of B vitamins was more significant for the patients with a history of cardio-cerebrovascular diseases.
  
  
  CONCLUSIONS
  Taking folic acid combined with vitamin B6 and B12 might have no significant effect on the incidences of cardio-cerebrovascular disease events and myocardial infarction, but could lower the risk of stroke and the level of homocysteine.
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Xi'an Jiaotong University, Xi'an 710061, China.
authors.forename: X
authors.initials: X
authors.lastname: Lan
authors.forename: S N
authors.initials: SN
authors.lastname: Dang
authors.forename: Y L
authors.initials: YL
authors.lastname: Zhao
authors.forename: H
authors.initials: H
authors.lastname: Yan
authors.forename: H
authors.initials: H
authors.lastname: Yan
mesh_terms: D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000401:mortality / Q000517:prevention & control*; D019587:Dietary Supplements; D004338:Drug Combinations; D005260:Female; D005492:Folic Acid / Q000097:blood / Q000627:therapeutic use*; D006710:Homocysteine / Q000097:blood; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D012306:Risk; D014805:Vitamin B 12 / Q000627:therapeutic use*; D025101:Vitamin B 6 / Q000627:therapeutic use*; D014803:Vitamin B Complex / Q000627:therapeutic use*
chemical_list: D004338:Drug Combinations; D006710:Homocysteine; D014803:Vitamin B Complex; D025101:Vitamin B 6; D005492:Folic Acid; D014805:Vitamin B 12