Age-related Changes in Human Conventional Semen Parameters and Sperm Chromatin Structure Assay-Defined Sperm DNA/chromatin Integrity.

Research question: What are the correlations between male age, traditional semen parameters, sperm DNA fragmentation index (DFI) and high DNA stainability (HDS) in a sufficiently large sample size? Design: Retrospective cohort study of 18,441 semen samples, with data divided into seven age groups according to male age: <= 25, 26-30, 31-35, 36-40, 41-45, 46-50 and >_51 years. Results: Age was negatively correlated with semen volume, total sperm count, motility and HDS, and positively correlated with sperm concentration and DFI (P < 0.001). After 35 years of age, semen volume and total sperm count began to decline. After 30 years of age, motility and HDS decreased consistently. Sperm concentration and DFI increased from 26-30 years of age. DFI was negatively correlated with sperm concentration, total sperm count, motility and normal morphology (P < 0.001) and positively correlated with semen volume and HDS (P < 0.001). HDS was negatively correlated with all parameters (P < 0.001) except semen volume (r = -0.013, P = 0.074) and DFI (r = 0.124, P < 0.001). Patients aged >_40 years had higher DFI than those aged <40 years in the entire cohort, in the abnormal semen parameters cohort, and in the normal semen parameters cohort (OR 2.145, 2.042, 1.948, respectively, P < 0.001). The >_40 years age group had a lower HDS than the <40 years age group in the entire cohort and abnormal semen parameters cohort (OR 0.719, 0.677, respectively, P < 0.001). Conclusions: Ageing is a negative effector of sperm quantity and quality, and routine sperm parameters have weak but significant correlations with sperm DNA/chromatin integrity.