Dear all,
I try to figure out how the Cholesterol Treatment Trialists’ (CTT) Collaboration calculated their metaanalysis but I have some trouble to reproduce the results.
According to the Baseline characteristics table and Figure 1 of the paper (Lancet. 2010 Nov 13;376(9753):167081.):

21 trials comparing statin with control were analyzed

the median followup was 4.8 years

the number of events / patients in the control group was 8934 / 64 782

the number of events / patients in the statin group was 7136/64 744
Dividing the number of events by the number of patients per group leads me to an event rate of 11.02% and 13.79% for the control and statin group, respectively.
Maybe it is naïve (assuming a continuous and linear relationship between event occurrence and time), but I then divided these rates by the median followup of 4.8, leading to event rates per anno of 2.87% and 2.30%, respectively.
However, the authors depicted per anno rates of 3.6% and 2.8%, respectively.
Moreover, the unweighted risk ratio calculated based on the abovementioned numbers is 0.80 and not 0.78 as the depicted subtotal treatment effect in Figure 1.
Most likely, I am just naïve and my statistical calculations are wrong. Therefore, I would be happy to get some expert support/guidance here!
In the slide deck provided on the CCT website, the authors present the 5year risk of an event. Is it possible to calculate this measure based on the published data (without individual patient data)?
I am looking forward to your replies.