Table 2.

Newcastle-Ottawa Scale for risk of bias assessment of cohort studies included in the meta-analysis

Study	Selection				Comparability	Outcome			Overall
	Representativeness of exposed cohort	Selection of non-exposed	Ascertainment of exposure	Outcome not present at start		Assessment of outcome	Adequate follow-up length	Adequacy of follow-up
Chu-Hsu Lin 2016 [19]	☆	★	★	★	★	★	★	★	7
Wojciech Pluskiewicz 2016 [20]	☆	★	★	☆	★★	★	★	★	7
Nadia Afrin 2016 [21]	★	★	★	★	★	★	★	★	8
Nadia Afrin 2018 [22]	★	★	★	☆	★	★	★	★	7
B. Drozdzowska 2013 [23]	★	★	★	★	★	★	★	★	8
Yuksel Ersoy 2009 [24]	☆	★	★	★	★	★	★	★	7
F. Hita-Contreras 2013 [25]	☆	★	★	★	★★	★	★	★	8
Kerri M. Winters-Stone 2011 [26]	☆	★	★	★	★	★	★	☆	6
Shawna Follis 2018 [27]	☆	★	★	★	★★	★	★	★	8
Kaisa M. Randell 2001 [28]	★	★	★	★	★★	★	★	★	9
Abdulrahim A. Rouzi 2015 [29]	★	★	★	★	★★	★	★	★	9

★, score of 1; ★★, score of 2; ☆, score of 0