Table 1.

Detailed Newcastle–Ottawa Scale of each included cohort study

Study	Representativeness of exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study	Comparability of cohorts on the basis of the design or analysis	Assessment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of follow-up of cohorts	Total quality score
Lara et al.	1	0	1	1	1	1	0	1	6
Bogani et al.	0	0	1	1	0	1	0	1	4
Mehta et al.	1	0	1	1	1	1	1	1	7
Dai et al.	1	1	0	1	2	1	0	1	7
Yang et al.	1	0	1	1	2	1	0	1	7
Suh-Burgmann et al.	1	0	1	1	0	1	0	0	3
Tsibulak et al.	1	1	0	1	1	1	0	1	6
Dursun et al.	1	0	0	1	0	1	1	1	5
De Santiago et al.	1	0	0	1	0	1	1	0	4

Score 0–1 for selection and outcome categories. Score 0–2 for comparability. Maximum score: 9