Table 5.

Risk of bias assessment of included cohort studies.

First author and published year	Items on SIGN checklist
	1	2	3	4	5	6	7	8	9	10	11	12	13	14	Total	Qualityb
Al-Sayegh, 201088	1	1	1	0	1	0	1	0	0	1	1	0	0	1	8	A
Peterson, 201489	1	0	0	0	1	0	1	0	1	1	1	1	1	0	8	A
Hastings, 201690	1	0	1	0	0	0	1	0	1	1	1	0	1	0	7	L
Skarica, 201892	1	0	0	0	0	0	1	0	0	0	0	0	0	0	2	U
Haavik, 201691	1	0	0	0	0	0	1	1	0	0	0	0	1	0	4	U

SIGN, Scottish Intercollegiate Guideline Network

^a,bSee Figure 4 for Quality assessment SIGN checklist items^a and scoring^b for cohort studies