Several studies have investigated the association of MMP‐9 gene polymorphisms with carotid atherosclerosis and the risk of IS or HT (Ho et al., 2015; Lin et al., 2012; Nie, Wang, & Tang, 2014; Yuan et al., 2013; Zhang, Cao, Xu, Li, & Xu, 2015). Here, MMP9 is linked to hematocrit.