Table 2.

Quality of bias assessment of the included papers in accordance with the Newcastle-Ottawa scale.

Study	Selection				Comparability†	Exposure
	Case definition	Representativeness of the cases	Selection of controls	Definition of controls	Comparability of cases and controls	Ascertainment of exposure	Same method of ascertainment	Nonresponse rate
Ho et al. 2021	—	—	—	—	—	∗	—	—
Carmona-Maurici et al. 2020	—	∗	—	—	—	∗	—	—
Coimbra et al. 2019	—	—	—	∗	—	∗	—	—
Gómez-Martín et al. 2018	—	—	—	—	∗	∗	—	—
Kelly et al. 2016	—	—	—	—	—	∗	—	—
Van der Schueren et al. 2015	—	—	—	∗	∗	∗	—	—
Müller-Stich et al. 2015	—	—	—	—	—	∗	—	—
Martín-Rodríguez et al. 2014	—	—	—	—	—	∗	—	—
Julve et al. 2014	—	—	—	—	—	∗	—	—
Garrido-Sánchez et al. 2008	—	∗	—	∗	—	∗	—	—
Uzun et al. 2004	—	—	—	—	—	∗	—	—

^†Only for comparability a maximum of two stars can be given.