Diurnal and seasonal changes in semen quality of men in subfertile partnerships

ABSTRACTCircadian and circannual rhythms influence not only the environment, but also human physiology. In times of increasing numbers of couples struggling with infertility, and thus increasing demand for successful assisted reproduction, the aim of our study was to evaluate circadian and circannual rhythms and their association with semen quality. A total of 12 245 semen samples from 7068 men, collected at the andrology laboratory of the Department of Reproductive Endocrinology, University Hospital Zurich, between 1994 and 2015, were uniformly analysed in terms of sperm concentration, total sperm count, progressive motility and normal morphology. On the basis of these four parameters, we retrospectively examined the circadian and circannual changes of semen quality. The Mann–Whitney U test and multiple linear regression analysis were used for the statistical evaluation. The semen samples collected in the early morning before 7:30 a.m. showed the highest levels in sperm concentration, total sperm count a...