APOE and obstructive sleep apnea syndrome: The e4 variant of APOE, is the largest known genetic risk factor for AD in a variety of ethnic groups and is also reported to be associated with the progression and severity of OSA, and cognitive dysfunction (Roses, 1996; Tardiff et al., 1997; Kadotani et al., 2001; Gottlieb et al., 2004; Conejero-Goldberg et al., 2014; Uyrum et al., 2015; Spira et al., 2017; Burke et al., 2018).