Table 2.

Quality assessment of included studies

Characteristics		Number of studies (%)a
Clear cause (ie, intervention of interest) and effect (ie, outcome of interest)	Yes	11 (100)
	No	0 (0)
	Unclear	0 (0)
Potential participants included in any comparisons are similar	Yes	10 (91)
	No	1 (9)
	Unclear	0 (0)
Potential participants included in any comparisons are receiving similar intervention, other than the exposure or intervention of interest	Yes	4 (36)
	No	5 (46)
	Unclear	2 (18)
Has control group	Yes	0 (0)
	No	10 (91)
	Unclear	1 (9)
Has multiple measurements of the outcome both pre- and post-the intervention or exposure	Yes	2 (18)
	No	6 (55)
	Unclear	3 (27)
Complete follow-up or if incomplete, the differences between groups in terms of their follow-up were adequately described and analyzed	Yes	0 (0)
	No	0 (0)
	Unclear	1 (9)
	NA	10 (91)
Outcomes of eligibility prescreening included in any comparisons measured in the same way	Yes	9 (82)
	No	1 (9)
	Unclear	1 (9)
Outcomes were measured in a reliable way	Yes	5 (45.5)
	No	5 (45.5)
	Unclear	1 (9)
Appropriate statistical analysis was used	Yes	9 (82)
	No	1 (9)
	Unclear	1 (9)
Authors disclose the presence or absence of potential conflict of interest	Yes	9 (82)
	No	1 (9)
	Unclear	1 (9)
Study quality rating	Low (1–4)	3 (27)
	Moderate (5–7)	7 (64)
	High (8–10)	1 (9)

NA: not applicable.

^aOut of 11 included studies.