High prevalence of isolated sperm DNA damage in infertile men with advanced paternal age.

BACKGROUND: Sperm DNA damage is associated with male infertility, lower pregnancy rates and pregnancy loss. OBJECTIVE: The primary aim of our study was to evaluate the prevalence of sperm DNA damage in younger and older men with normozoospermia. DESIGN, SETTING AND PARTICIPANTS: We obtained semen from 277 consecutive non-azoospermic men presenting for sperm DNA testing. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The main outcome measures included sperm % DNA fragmentation index (%DFI, using sperm chromatin structure assay), sperm concentration, motility and morphology, and, paternal age. RESULTS AND LIMITATIONS: Sperm % DFI was positively correlated with paternal age (r = 0.20, P < 0.001) and inversely correlated % progressive motility (r = -0.16, P = 0.01). Sperm %DFI was significantly higher in older (≥40 years) compared to younger (<40 years) normozoospermic men (17 ± 13 vs. 12 ± 8, respectively P = 0.008), whereas, sperm concentration, progressive motility and morphology were not significantly different in these two groups. Moreover, the prevalence of high levels of sperm DNA damage (>30 % DFI) was significantly higher in older compared to younger normozoospermic men (17 % vs. 3 %, respectively, P < 0.001). CONCLUSION: The data indicate that a conventional semen analysis can often fail to detect a defect in spermatogenesis (high %DFI) in older men and suggest that infertile couples with advanced paternal age, including those with normal semen parameters, should consider sperm DNA testing as part of the couple evaluation.