Table 1

Key features of the included pooled  analyses/meta-analyses   and systematic reviews (PMASRs)

Included PMASRsN (%)Range
MinimumMaximum
Included PMASRs, n42 (100)
Included meta-analysis, n31 (74)
Included systematic review and meta-analysis, n11 (26)
Systematic review and meta-analysis that only included prospective cohorts, n1 (2)
PMASRs that only included prospective cohorts, n7 (17)
Publication year19912017
Funding (industry-funded PMASRs)2 (5)
Funding (non-industry-funded PMASRs)26 (62)
Funding (no funding/not reported)14 (33)
Age (years)8107
PMASRs that used random-effects model, n25 (60)
PMASRs that used fixed-effects model, n3 (7)
PMASRs that used random-effects and fixed-effects models, n8 (19)
PMASRs that reported subgroup analysis, n26 (62)
PMASRs that reported publication bias, n23 (55)
PMASRs that reported meta-regression, n14 (33)
PMASRs that reported Grading of Recommendations Assessment, Development and Evaluation (GRADE), n0 (0)
PMASRs that reported risk of cancer as outcome, n40 (95)
PMASRs that reported all-cause mortality as outcome, n1 (2)
PMASRs that reported cancer-specific mortality as outcome, n3 (7)
AMSTAR scores of PMASRs (out of 11)18
AMSTAR, Assessing the Methodological Quality of Systematic Reviews.