Table 2.

Methodological quality assessment of the eligible studies

Study	Random sample or whole population	Unbiased sampling frame	Adequate sample size (> 300 subjects)	Standard measures	Outcomes measured by unbiased assessors	Adequate response rate (> 70%) and refusers described	Confidence intervals and subgroups analysis	Study subjects described	Total score
Bryant et al. [46]	0	0	0	1	1	1	1	1	5
Bryant et al. [8]	0	0	0	1	1	1	1	1	5
Fuglsang et al. [52]	0	0	0	1	0	1	1	1	4
Jones et al. [47]	0	0	0	1	1	1	1	1	5
Hamanaka et al. [53]	0	0	0	1	1	1	1	1	5
Yasan et al. [14]	0	0	0	1	1	1	1	1	5
van den Heuvel et al. [54]	0	0	0	1	0	1	1	1	4
Winston et al. [55]	0	0	0	1	1	1	1	1	5
Bryant et al. [56]	0	0	0	1	0	1	1	1	4
Winston et al. [13]	1	1	1	1	0	1	1	1	7
Salmon et al. [15]	0	0	0	1	1	1	1	1	5
Meiser-Stedman et al. [16]	0	0	1	1	1	0	1	1	5
Haag et al. [17]	0	0	0	1	1	1	1	1	5