Table 2.

Quality assessment according to Newcastle-Ottawa Scale

Study	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Total
Bonthuis et al. (2010) [21]	1	1	1	1	2	1	1	1	9
Breslow et al. (2000) [22]	1	1	1	1	2	1	1	0	8
Chow et al. (1992) [23]	1	1	1	1	2	0	1	1	8
Kelemen et al. (2005) [24]	0	1	1	1	2	0	1	0	6
Kojima et al. (2004) [25]	1	1	1	1	2	1	1	1	9
Matsumoto et al. (2007) [26]	1	1	1	1	2	1	1	1	9
Park et al. (2007) [27]	1	1	1	1	2	1	1	0	8
Praagman et al. (2015) [28]	1	1	1	1	2	1	1	1	9
Sharma et al. (2013) [29]	1	1	1	1	2	1	1	0	8
Song et al. (2013) [30]	0	1	1	1	2	1	1	1	8
Wang et al. (2015) [31]	1	1	1	1	2	1	1	1	9