Table 2:

Newcastle–Ottawa Scale checklist

Study ID	Selection				Comparability		Outcome
	Representativeness of exposed cohort?	Selection of non-exposed cohort?	Ascertainment of exposure?	Demonstration that outcome of interest was not present at start of study?	Study controls for age and sex?	Study controls for additional risk factors?	Assessment of outcome?	Was follow-up long enough for outcome to occur?	Adequacy of follow-up of cohorts?
Aksoy et al. [9]	√	√	√	–	√	√	–	√	√
Bannay et al. [10]	√	√	√	–	√	√	√	√	√
Cabell et al. [11]	–	√	√	√	√	√	–	–	√
Funakoshi et al. [12]	–	√	√	–	√	√	–	√	√
Hill et al. [13]	–	√	√	–	√	√	√	–	√
Lalani et al. (2010) [2]	√	√	√	√	√	√	√	–	√
Lalani et al. (2013) [7]	√	√	√	√	√	√	√	–	√
Mourvillier et al. [14]	–	√	√	–	√	√	–	–	√
Ohara et al. [15]	√	√	√	–	√	√	–	–	√
Sy et al. [16]	–	√	√	–	√	√	–	√	√
Thuny et al. [17]	√	√	√	–	√	√	√	–	√
Wang et al. [20]	√	√	√	–	√	√	√	–	√
Wang et al. [21]	–	√	√	–	√	√	√	–	–
Jia et al. [22]	–	√	√	–	√	√	–	–	–
Vikram et al. [19]	√	√	√	√	√	√	√	–	√
Tleyjeh et al. [18]	–	√	√	–	√	√	–	–	√