Objective: To describe the intraindividual variation in semen parameters.
Design: Prospective, longitudinal study.
Setting: Academic research environment.
Patient(s): Twenty-seven healthy men, followed monthly for 16 months.
Intervention(s): Monthly semen samples were collected, as well as information regarding duration of abstinence, febrile episodes, and ejaculatory frequency.
Main outcome measure(s): Sperm concentration, percentage immotile spermatozoa, and percentage morphologically normal spermatozoa.
Result(s): There were no significant seasonal variations in sperm concentration, motility, or morphology. The ejaculatory frequency was significantly higher during spring compared with winter months. There was a significant difference in sperm concentration with respect to having one, two, or more than two ejaculations during a 7-day period before the abstinence period. Sperm motility and morphology were not affected by ejaculatory frequency. Duration of abstinence, ejaculatory frequency, and fever accounted only little for the high intraindividual variation in individual semen parameters. Three semen samples compared with two reduced the intraindividual variations as follows: sperm concentration from 41% to 33.5%, percentage normal spermatozoa from 6.9% to 5.7%, and percentage immotile spermatozoa from 19% to 15.5%.
Conclusion(s): Ejaculatory frequency but not season significantly affected sperm concentration. Most of the intraindividual variations in semen parameters could not be explained by duration of abstinence, fever, or ejaculatory frequency.