Table 2. Risk of bias in the cross-sectional and retrospective studies assessed using the Newcastle-Ottawa Scale.

* corresponds to one score

Author, year	Selection (Max = 4)	Comparability (Max = 2)	Exposure (Max = 3)	Overall quality score (Max = 9)
Nieuwenhuysen et al., 2003 [8]	**	**	**	6
Opdam et al., 2007 [10]	***	**	***	8
Opdam et al., 2010 [11]	****	**	**	8
McCracken et al., 2013 [12]	***	**	***	8
Al-Asmar et al., 2023 [14]	**	**	*	5
Santos et al., 2023 [15]	**	**	**	6