The association between methamphetamine use and number of sexual partners in men who have sex with men: a systematic review and meta-analysis

Table 2 Methodological Quality scores included cohort studies using Newcastle–Ottawa scale

Study	Selection			Comparability	Outcome/Exposure		Study score/9
Study	Representativeness of the sample	Non-respondents	Ascertainment of the exposure (risk factor)	The subjects in different outcome groups are comparable, based on the study design or analysis. Confounding factors are controlled	Assessment of the outcome/Exposure	Statistical test
Hirshfield et al. (2004) [21]	*	*	*	**	**	-	7
Fernandez et al. (2007) [24]	*	*	*	**	**	-	7
Drumright et al. (2009) [22]	*	*	*	**	**	*	8
Brown et al. (2017) [23]	*	*	**	*	*	*	7
Planky et al. (2007) [20]	*	*	*	**	*	*	7
Prestage et al. (2009) [18]	*	*	*	**	*	*	7
Hoenigl et al. (2015) [17]	*	*	*	**	**	*	8
Piyaraj et al. (2018) [19]	**	*	*	**	**	*	9