Demirkol MK, Yıldırım A, Gıca S, et al. - This study was undertaken to investigate the effect of shift work on semen parameters together with the effect of sleep quality in men attending infertility clinic. Individuals were classified into two groups as follows: 104 shift worker men and 116 non shift worker men. Researchers observed a higher rate of oligozoospermia and poor sleep quality and a lower mean normal morphology percentage in shift workers than nonshift workers. It has been reported that infertile shift workers had a lower percentage of normal morphology and higher rates of oligozoospermia and poor sleep quality. As per the findings, considering that shift workers have lower sleep quality, it appears that shift working negatively affects the circadian rhythm.