Bjelakovic G, Nikolova D, Wetterslev J, Gluud C. Comment to: ‘Meta-analysis of long-term vitamin D supplementation on overall mortality’. PLOS ONE. 2014.

Figure 1. Intervention effect of vitamin D3 and vitamin D2 vs placebo or no intervention on mortality.
Figure 2. Trial sequential analysis of 20 vitamin D3 trials with low risk of bias. The diversity-adjusted required information size (DARIS) was calculated based on mortality in the control group of 10%; relative risk reduction of 5% in the experimental group; type I error of 5%; and type II error of 20% (80% power). No diversity was noted. The required information size was 110,505 participants. The cumulative Z-curve (blue line) did not cross the trial sequential monitoring boundaries for benefit (red line) at any time. Accordingly, the crossing of the conventional statistical 5% boundary (the horizontal brown line) may be due to random errors.