Table 2.

Quality assessment of the included studies based on the NOS checklist (adapted for cross sectional studies)

Author, Year	QUESTION 1	QUESTION 2	QUESTION 3	QUESTION 4	QUESTION 5	QUESTION 6	QUESTION 7	Overall
Nakazato et al., 2002	*	*	*	**		*	*	7
Nakazato et al., 2006		*	*	**	*	*		6
Nakazato et al., 2009	*	*	*	**	*		*	7
Yamada et al., 2012	*		*		*	*	*	5
Dmitrzak-Weglarz et al., 2013	*	*	*	**	*	*		7
Zwipp et al., 2014	*	*		*	*	*	*	6
Eddy et al., 2015	*	*	*		**	*	*	7
Homan et al., 2015	*		*	**	*		*	6
Rybakowski et al., 2017	*	*	*	*	**		*	7
Matsumoto et al., 2017	*	*	*	**		*	*	7
Mancuso et al., 2020	*	*	*	**	*		*	7
Tyszkiewicz-Nwafor et al., 2020	*	*	*	*	*		*	6
Borsdorf et al., 2021	*	*	*	*	**	*	*	8
Keeler et al., 2022	*	*		*	**		*	6

Selection: Questions 1 to 4, Comparability: Question 5, Outcome: Questions 6 and 7

*, ** The NOS checklist uses a "star system" to assess the quality of studies, with the number of stars indicating the overall score in that particular domain, i.e., Selection, Comparability, and Outcome