Is the quality of donated semen deteriorating? Findings from a 15 year longitudinal analysis of weekly sperm samples.

Background: Studies suggest that global semen quality is declining, but the debate remains open owing to geographic variation.

Objectives: To evaluate temporal trends of sperm parameters - namely concentration, motility and total motile sperm count - in sperm donated during the period 1995-2009.

Methods: In a retrospective longitudinal cohort study we analyzed the sperm count and motility of 2182 semen samples provided on a weekly basis by 58 young, healthy, fertile, university-educated, paid donors.