[Impact of seasonal variation on pre- and post-thaw donor semen parameters]

To investigate the relationship of seasonal variation with pre- and post-thaw semen parameters as well as the cryosurgical of human spermatozoa.

A total of 6 414 semen samples were collected from 1 135 donors aged 22 - 32 years by Zhejiang Human Sperm Bank, and divided into spring, summer, autumn and winter groups according to the time of collection. All the samples underwent routine seminal analysis, and the sperm parameters were compared between different seasons. The sperm specimens were cryopreserved in aliquots and analyzed after thawing.

The semen volume was (2.92 +/- 1.17) ml in spring, significantly higher than in summer, autumn and winter ([2.71 +/- 1.07 ], [2.74 +/- 1.15] and [2.83 +/- 1.15] ml, P < 0.05). Sperm density was the highest in autumn ([105.60 +/- 39.76] x 10(6)/ml) as compared with the other three seasons ([101.18 +/- 40.16] x 10(6)/ml, [93.54 +/- 35.10] x 10(6)/ml, and [101.29 +/- 38.37] x 10(6)/ml, P < 0.05). The sperm progressive motility was the highest in spring ([58.49 +/- 10.04] %) and the cryosurgical of sperm the lowest in summer, with statistically significant differences from the other groups (P < 0.05).

Seasonal variations affect human semen quality and cryosurgical of sperm. The semen volume, the percentage of progressive motile sperm, the cryosurgical of sperm, and the post-thaw density of progressive motile sperm are higher in spring than during the rest of the year.