Seasonal changes are assumed to affect various sperm characteristics based on photoperiods, temperature, and air pollution. According to the literature, most studies were performed on populations of Western countries, and there are limited studies performed in the Middle East with variable results. This study evaluated the seasonality of sperm characteristics among men of reproductive age in an andrology center in Kerman, Iran, where the seasonal temperature varies significantly, with average temperatures ranging from 50 °F (10 °C) to 75.2 °F (24 °C). We retrospectively evaluated the sperm analysis test record. Sperm samples were obtained from 2,948 men during 10 years, excluding those with azoospermia. Samples were assessed for volume, concentration, motility, and morphology according to the World Health Organization (WHO) criteria. We performed a comprehensive comparative literature review of the studies investigating the association between seasonal variation and sperm quality. The mean semen volume was higher in the summer compared with other seasons (p = .04). The mean percentage of sperm motility was higher in the spring and less in winter (p = .03). Sperm morphology-related parameters, measured by the percent of normal morphology, were significantly better in winter (p = .03). Our findings suggest seasonality of sperm characteristics among men of fertility age. Semen volume, motility, and morphology were affected by the photoperiod of reproductive seasons. Results might support the influential role of seasonal variations in the possibility of fertility, especially among those using assisted reproductive technologies and those with oligospermia.
Keywords: fertility; seasonal variations; sperm analysis; sperm quality.