Table 2.

Summary of review inclusion and exclusion criteria

	Inclusion criteria	Exclusion criteria
Study or publication type	Peer-reviewed systematic reviews of primarily quantitative data with or without meta-analysis (or similar statistics).40 44 Reviewed literature identified using a systematic structured search of bibliographic databases. Ideally, the review has been conducted and reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses54 and/or the methods used are explicit, prespecified, transparent and reproducible.40	Reviews excluded if they: (i) are not peer-reviewed, or (ii) do not detail systematic and prespecified protocols, or (iii) are commentaries rather than critiques.44 Case reports, comments, editorials, guidelines, letters or practice guidelines.
Population	Individuals included in the studies within the reviews are primarily involved in a population-representative or community cohort (note: if the review is not primarily focused on free-living community or population cohort studies, then the community/population cohort studies must at least be largely presented/reviewed independently from other study types also reviewed). Cohort is longitudinal, observational, prospective or retrospective (eg, data linkage). Not limited to high-income countries.	Individuals included in studies in the reviews/meta-analyses are primarily involved in clinical cohorts, cross-sectional, case–control studies, randomised controlled trials, or in population/community cohorts that have been selected on pre-existing criteria (eg, disease free at time of recruitment).
Intervention/ exposures	Examination of potential intervention targets for preventing early death, where intervention target has been measured prior to the outcome. Further detail in ‘Intervention targets/exposures’ section.	Intervention targets measured prior to birth or concurrently/at the same time as the outcome. Reviews that focus on predictors (ie, not suited to intervention) of mortality, rather than intervention targets (ie, causes). Or where the focus is unclear.
Comparator	Not limited by comparator populations.	NA
Outcome	Review synthesises primary papers examining any cause of mortality during or after age 15 years (even if some, but not all, mortality exceeds 60 years). Following which, regardless of publication date, each relevant primary paper within each included review will be sourced, and also included in primary paper data synthesis if participants are aged between ≥15 years and ≤60 years. Further detail in ‘Outcomes’ section.	Review synthesises primary papers examining mortality measured only before age 15, or only after age 60. Regardless of publication date, each relevant primary paper within each included review will be sourced and the primary paper (not the review) will be excluded from primary paper data synthesis if mortality is only measured before age 15 or after age 60.
Publication date	Because intervention targets for preventing death vary with changing social, political and economic conditions, to ensure reviewed targets are relevant today we will only include reviews published during/after 2012.	Published before 2012.