Study selection 
Once the search was done, two authors, MC and MP, applied separately the eligibility criteria to decide which studies include. Any disagreement between the authors was solved through discussion with a third author, EM, to try to reach an agreement. In case of not getting access to a complete text or abstract, we attempted to get in contact with the main investigator to get a copy of the study. With the results of the search in each base and with the subsequent eligibility criteria application a flow chart was made.