Table 2.

Quality assessment of the included studies

	Selection				Comparability		Outcome measurement			Total score
	Patient definition	Representat-iveness of patients	Selection of controls	Definition of controls	Age	Gender/ education	Ascertainment of outcome	Same method of ascertainment for case and control	Non-response rate
Graae et al. (1996) [55]	1	0	1	1	1	1	1	1	0	7
Arikan et al. (2019) [56]	1	0	0	1	0	0	1	1	0	4
Benschop et al. (2019) [57]	1	0	1	1	0	1	1	1	0	6
Roh et al. (2020) [58]	1	0	1	1	0	0	1	1	0	5
Iznak et al. (2021) [59]	1	0	1	1	0	1	1	1	1	7
Krepel et al. (2021) [60]	1	1	1	1	0	1	1	1	0	7
Amico et al. (2023) [61]	1	0	0	0	0	0	1	1	1	4
Bankwitz et al. (2023) [62]	1	0	0	1	1	1	1	1	1	7
Jiang et la. (2023) [63]	1	0	1	1	1	1	1	1	0	7
Ozger et al. (2023) [64]	1	0	0	1	0	0	1	1	0	4
He et al. (2024) [65]	1	0	0	0	1	0	1	1	0	4