Data extraction and synthesis
Two investigators (MBE and CJG) independently selected eligible
systematic review. Disagreement was resolved by discussion with another
investigator (VM). Data on all-cause mortality was sought, synthesized,
analysed, critically examined and interpreted from systematic reviews
and primary studies. We extracted odds ratio (ORs), relative risk (RRs),
or hazard ratios (HRs) from the included studies with 95% CI. We did
not reanalyze the authors’ original data or conduct new meta-analyses by
combining studies.