Table 2.

Results of quality assessment by the Newcastle-Ottawa Scale for case-control studies

Study	Selection				Comparability	Exposure			Total score
	Adequate definitionof the cases	Representativenessof the cases	Selection ofcontrols	Definition ofcontrols	Control forimportant factors	Ascertainmentof exposure	Same method of ascertainmentfor cases and controls	Non-responserate
Marozik et al. [19]	√		√	√	√	√	√	√	7
Techapatiphandee et al. [12]	√	√		√	√	√	√	√	7
Ahmad et al. [20]	√	√		√	√√	√	√	√	8
Moran et al. [21]	√				√√	√	√	√	6
Marozik et al. [22]	√			√	√√	√	√	√	7
Gonzalez et al. [23]	√	√		√	√	√	√	√	7
Efesoy et al. [24]	√		√	√	√	√	√		6
Zhang et al. [13]	√			√	√	√	√	√	6
Mansour et al. [26]	√			√	√	√	√	√	6
Tanriover et al. [25]	√	√		√	√√	√	√	√	8
Musumeci et al. [27]	√			√	√	√	√	√	6
Mencej et al. [28]	√	√		√	√	√	√	√	7
Seremak et al. [29]	√			√		√	√	√	5
Perez et al. [30]	√	√	√	√	√	√	√	√	8
Uysal et al. [31]	√			√		√	√	√	5
Quevedo et al. [32]	√		√	√		√	√		5
Wengreen et al. [33]	√	√	√	√	√√	√	√	√	9
Mitra et al. [35]	√	√		√	√	√	√	√	7
Garnero et al. [34]	√			√	√	√	√		5
Duman et al. [36]	√			√	√√	√	√	√	7
Zhu et al. [47]	√		√	√	√	√	√	√	7
Douroudis et al. [37]	√			√	√	√	√	√	6
Borjas-Fajardo et al. [39]	√			√		√	√	√	5
Chen et al. [48]	√		√	√		√	√	√	6
Lisker et al. [38]	√	√		√	√	√	√	√	7
Zajickova et al. [40]	√	√		√	√	√	√	√	7
Leng et al. [49]	√		√	√		√	√	√	6
Ly et al. [50]	√		√			√	√	√	5
Pollak et al. [41]	√			√		√	√	√	5
Valimaki et al. [42]	√		√	√		√	√		5
Aerssens et al. [43]	√	√	√	√	√	√	√	√	8
Garrofe et al. [44]	√		√	√	√	√	√	√	7
Zhang et al. [51]	√			√	√	√	√	√	6
Gennari et al. (1999)	√	√		√	√	√	√	√	7
Gomez et al. [45]	√			√	√√	√	√		6
Ramalho et al. [54]	√			√	√√	√	√	√	7
Gennari et al. [46]	√		√	√	√√	√	√	√	8
Zhang et al. [52]	√		√	√		√	√	√	6
Vandevyver et al. [55]	√			√	√√	√	√	√	7
Houston et al. [56]	√				√√	√	√	√	6
Berg et al. [11]	√			√	√	√	√		5
Yanagi et al. [53]	√		√	√		√	√		5
Melhus et al. [1]	√		√			√	√	√	5

√: matched the condition, scored one point