Table 3.

Newcastle–Ottawa quality assessment scale and analysis of observational studies

	Sample representativeness	Sample size	Nonrespondents	Ascertainment of exposure	Comparability	Assessment of outcome	Statistical test
Alegret et al. 2014	Selected	*	*	**	*	*	*
Benzimra et al. 2018	Selected	*	*	**	*	*	*
Carrothers et al. 2014	Selected	*	*	‐	*	*	‐
Castellucci et al. 2015	Selected	*	*	**	*	*	*
De Caterina et al. 2018	Selected	*	‐	**	*	*	‐
Fernandez et al. 2018	Selected	*	*	**	*	*	‐
Hanon et al. 2016	*	*	‐	**	*	*	‐
Keita et al. 2017	Selected	*	*	**	*	*	*
Koretsune et al. 2018	Selected	*	*	**	*	*	‐
Larochelle et al. 2018	Selected	*	‐	**	*	*	*
Marquez‐Contreras et al. 2017	*	*	*	*	*	*	‐
Muruaga et al. 2017	Selected	*	‐	**	*	*	*
Obamiro et al. 2018	*	*	*	**	*	*	*
Okumura et al. 2018	Selected	*	‐	**	*	*	*
Stephenson et al. 2018	*	*	*	**	*	*	*

7–8 * = good studies.

5–6 * = satisfactory studies.

0–4 * = unsatisfactory studies.