Table 1.

Systematic review characteristics

	Total reviews (N = 17)
Reviews with meta-analysis*: n (%)	16 (94.1%)
Pre-specified subgroups
Reviews with pre-specified subgroupsa	13 (76.5%)
Planned covariates for subgroup analysis: median (min, max)	3 (0, 6)
Reviews with subgroup analyses conducted: n (%)b	7 (41.2%)
Covariates used in subgroup analyses: median (min, max)	2 (1, 6)
Reviews with subgroup effects**: n (%)c	3 (17.6%)
Covariates in subgroup analyses: median (min, max)	2 (1, 3)
Post hoc subgroup analyses
Reviews with post hoc subgroup analysesd	5 (29.4%)
Reviews with post hoc subgroup effects: n (%) e	4 (23.5%)
Covariates used in subgroup analyses: median (min, max)	1 (1, 5)
Any subgroup analyses performed, pre-specified, or Post Hoc
Reviews with any subgroup analysesf	9 (52.9%)
Covariates used in subgroup analyses: median (min, max)	2 (1, 11)
Number with subgroup effects: n (%)	5 (29.4%)
No subgroup analyses performed
Reviews with no subgroup analyses performedg	8 (47.1%)
Reasons for not conducting subgroup analyses: n (%)
Insufficient data/studies	4 (23.5%)
Not planned	4 (23.5%)

*One review [39] did not conduct meta-analysis due to insufficient studies

a[26, 29–40]

b[29, 30, 33, 35, 36, 38, 39]

c[35, 38, 39]

d[24, 30, 31, 35, 38]

e[30, 31, 35, 38]

f[24, 29–31, 33, 35, 36, 38, 39]

g[25–28, 32, 34, 37, 40]

**Sub-group effects were characterized by p ≤ 0.05 for interaction terms, using Chi² test for subgroup differences. This does not include 3 reviews which presented effects within a subgroup but did not test for interaction effects.