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. Results: Despite the lowering of criteria for sperm parameters satisfactory for donation that were implemented in 2004, 38% of applicants for sperm donation are now rejected based on semen quality as compared to a third of applicants 10-15 years ago (P < 0.001). If the old strict criteria were in place 88% of candidates would be rejected today (P < 0.0001). Over the study period, the average sperm parameters dropped from a concentration of 106 ± 25 million spermatozoa/ml with 79% ± 4.3% motility to 68 ± 14 million/ ml with 66% ± 4.5% motile sperm (P < 0.0001, P < 0.0001, respectively). The total motile sperm count per ejaculate also decreased, from 66.4 ± 18.2 million to 48.7 ± 12 million (P < 0.005). When the previous criteria were implemented for the analysis of the latest group of sperm donors, only 18% of donors had an acceptable sperm quality, with an average concentration of 87 ± 12 million spermatozoa/ml, 73% ± 2.6% motile sperm and total motile sperm count of 53.1 ± 3.8 million per ejaculate - still significantly lower than 15 years ago (P = 0.01, P = 0.003, P = 0.058 respectively). Conclusions: The rapid deterioration of sperm quality among fertile semen donors is alarming and may lead to cessation of sperm donation programs.