Comments on all the required elements related to ethical research "We used reported event rates for all studies to compute cumulative odds ratio and p-value for re-admission rate and mortality. Pre-specified subgroup analysis was performed to assess the difference in readmission rate and mortality according to the length of follow-up. Summary effects were estimated using random effects models. Of 263 potentially relevant studies, a total of 20 studies (3469 patients) met our inclusion criteria a