CLOCK and Parkinson disease: The epigenetic clock has been widely described to be associated with detrimental health and a myriad of disorders including obesity, Down syndrome, Parkinson's disease, Huntington's disease, and cognitive and physical fitness in the elderly (Chen et al., 2016; Horvath et al., 2015; Horvath and Ritz, 2015; Levine et al., 2015; Marioni et al., 2015; Nevalainen et al., 2017; Quach et al., 2017).