TABLE IV.

Quality Assessment of the Included Case-Control Studies by the Newcastle-Ottawa Scale^†

Study	Selection				Comparability	Exposure
	Adequacy of Case Definition	Represen-tativeness of Cases	Selection of Controls	Definition of Controls	Comparability of Cases and Controls on the Basis of the Design or Analysis	Ascertainment of Exposure	Same Method of Ascertainment for Cases and Controls	Non-response Rate
Salmon et al.32 (2018)	*	*	*	*	**	*	*	X
Engelman et al.35 (2014)	*	*	*	*	**	*	*	X
Webster et al.36 (2014)	*	*	*	*	**	*	*	*
Mascarenhas et al.37 (2012)	*	*	*	*	**	*	*	*

^†Star (*) = item present, and X = item absent. A maximum of 1 star is possible for the Selection and Exposure domains, and a maximum of 2 stars for the Comparability domain.