title: Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis.
abstract: OBJECTIVE
  To investigate whether calcium supplements increase the risk of cardiovascular events.
  
  
  METHODS
  Patient level and trial level meta-analyses.
  
  
  METHODS
  Medline, Embase, and Cochrane Central Register of Controlled Trials (1966-March 2010), reference lists of meta-analyses of calcium supplements, and two clinical trial registries. Initial searches were carried out in November 2007, with electronic database searches repeated in March 2010.
  
  
  METHODS
  Eligible studies were randomised, placebo controlled trials of calcium supplements (>or=500 mg/day), with 100 or more participants of mean age more than 40 years and study duration more than one year. The lead authors of eligible trials supplied data. Cardiovascular outcomes were obtained from self reports, hospital admissions, and death certificates.
  
  
  RESULTS
  15 trials were eligible for inclusion, five with patient level data (8151 participants, median follow-up 3.6 years, interquartile range 2.7-4.3 years) and 11 with trial level data (11 921 participants, mean duration 4.0 years). In the five studies contributing patient level data, 143 people allocated to calcium had a myocardial infarction compared with 111 allocated to placebo (hazard ratio 1.31, 95% confidence interval 1.02 to 1.67, P=0.035). Non-significant increases occurred in the incidence of stroke (1.20, 0.96 to 1.50, P=0.11), the composite end point of myocardial infarction, stroke, or sudden death (1.18, 1.00 to 1.39, P=0.057), and death (1.09, 0.96 to 1.23, P=0.18). The meta-analysis of trial level data showed similar results: 296 people had a myocardial infarction (166 allocated to calcium, 130 to placebo), with an increased incidence of myocardial infarction in those allocated to calcium (pooled relative risk 1.27, 95% confidence interval 1.01 to 1.59, P=0.038).
  
  
  CONCLUSIONS
  Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction. As calcium supplements are widely used these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population. A reassessment of the role of calcium supplements in the management of osteoporosis is warranted.
authors.affiliation: Department of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92 019, Auckland 1142, New Zealand.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Bolland
authors.forename: Alison
authors.initials: A
authors.lastname: Avenell
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
authors.forename: Andrew
authors.initials: A
authors.lastname: Grey
authors.forename: Graeme S
authors.initials: GS
authors.lastname: MacLennan
authors.forename: Greg D
authors.initials: GD
authors.lastname: Gamble
authors.forename: Ian R
authors.initials: IR
authors.lastname: Reid
mesh_terms: D000328:Adult; D000368:Aged; D050071:Bone Density Conservation Agents / Q000008:administration & dosage / Q000009:adverse effects*; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000009:adverse effects*; D019587:Dietary Supplements / Q000009:adverse effects*; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000209:etiology*; D010024:Osteoporosis / Q000517:prevention & control; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D020521:Stroke / Q000209:etiology*; D014807:Vitamin D / Q000008:administration & dosage
chemical_list: D050071:Bone Density Conservation Agents; D002136:Calcium, Dietary; D014807:Vitamin D