CLOCK and Infertility: Moreover, Clock gene variants are associated with altered semen quality in men with idiopathic infertility (Shen et al. 2015; Zhang et al. 2012), and shift-working men show increased rates of oligozoospermia, reduced sperm count, and elevated infertility risk compared with non-shift workers (Demirkol et al. 2021; El-Helaly et al. 2010; Sheiner et al. 2002; Liu et al. 2020).