Information sources, search strategy, and study selection
MEDLINE, Embase, Cochrane Central Register of Controlled
Trials, CINAHL, clinicaltrials.gov, and Google
Scholar were searched using computerized search protocols
from database inception up to August 2015 (electronic
search strategies are included in Additional file 1).
The references of articles reviewed for eligibility were
hand-searched in duplicate for further potentially relevant
articles. Study investigators, study time period, population
characteristics, and study methodology were closely examined
to ensure that multiple reports of the same experimental
data were not included (Table 2). Two reviewers
(SO, IM) independently assessed study eligibility using
standardized, piloted eligibility forms. Provision was made
for arbitration by a third co-investigator (AFR) in the