Variation of semen quality in normal men

Area of Science:

• Reproductive biology
• Andrology
• Human reproductive health

Background:

• Semen analysis is crucial for assessing male fertility.
• Understanding variability in semen parameters is essential for accurate interpretation.
• Previous studies have explored factors influencing semen quality, but within-subject variability requires further elucidation.

Purpose of the Study:

• To quantify the variability in key semen analysis parameters.
• To investigate the potential influence of season on semen quality.
• To differentiate between within-subject and between-subject variations in sperm parameters.

Main Methods:

• Analysis of 673 semen specimens from seven healthy men over extended periods (72-324 weeks).
• Assessment of sperm concentration, ejaculate volume, motility, and motility index.
• Statistical analysis to determine the proportion of variance attributable to within-subject differences and seasonal effects.

Main Results:

• Significant sample-to-sample variation was observed in all assessed semen parameters.
• Within-subject differences accounted for the largest proportion of overall variance: sperm concentration (54%), ejaculate volume (59%), motility (96%), and motility index (74%).
• While seasonal changes in results were noted, no consistent trends were identified, and no evidence supported seasonal influence or methodological bias.

Conclusions:

• Individual biological variability is the primary driver of changes in semen analysis results over time.
• Seasonal variations do not appear to significantly impact semen quality parameters in healthy men.
• These findings underscore the importance of considering individual baseline values and longitudinal data in fertility assessments.