Seventeen studies were included: eight prospective cohort studies (n=271,214); eight RCTs (n=43,646, range 192 to 36,282 participants); and one nested case-control study (n=1,000). Follow-up periods ranged from 90 days to eight years. Four cohort studies were rated good, three fair and two poor. Four RCTs were rated fair and four poor.
Five studies of patients who received dialysis showed consistent reductions in cardiovascular mortality in those who received vitamin D supplements; one study of a general population showed no statistically significant reductions. Four studies of initially healthy persons found no differences in incidence of cardiovascular events between calcium supplement recipients and non recipients.
RCTs showed no statistically significant reductions in cardiovascular events with vitamin D supplementation (RR 0.90, 95% CI 0.77 to 1.05; two studies), calcium supplementation (RR 1.14, 95% CI 0.92 to 1.41; three studies) and a combination of vitamin D and calcium supplementation (RR 1.04 95% CI 0.92 to 1.18; two studies) compared with placebo. There was no evidence for publication bias or significant heterogeneity.