The effects of age on sperm quality: an evaluation of 1,500 semen samples

Objective: The aim of this study was to evaluate the effects of aging on semen quality in a population of infertile couples. Methods: A cross-sectional study of semen samples obtained from 1,500 men randomly selected from couples who attended an infertility clinic was conducted. The analyses were performed using Spearman's correlation and Mann-Whitney tests. The age groups consisted of men <= 35 years, from 36-45 years and > 45 years of age. The semen analysis was performed according to the WHO criteria, and morphology was evaluated using the motile sperm organelle morphology examination (MSOME). The percentages of normal spermatozoa and spermatozoa with large nuclear vacuoles (LNV, occupying > 50% nuclear area) were determined. The percentages of DNA fragmentation were assessed using the TUNEL assay. Results: A regression analysis revealed that the percentages of LNV spermatozoa and sperm DNA fragmentation positively correlated with age. Conversely, a regression analysis revealed that the percentage of normal sperm, sperm progressive motility and sperm vitality negatively correlated with age. As in the previous test, the analysis by age group showed that there was a significant reduction (P < 0.05) in the percentage of normal sperm, sperm progressive motility and sperm vitality as age increased. Conversely, the percentage of spermatozoa with LNVs and sperm DNA fragmentation significantly increased (P < 0.05) as age increased. Conclusion: Semen quality seems to be influenced by aging. The age-related decrease in sperm quality suggests that delaying childbearing, not only for women but also for men, may jeopardize reproductive capacity.