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

Sperm DNA damage is associated with male infertility, lower pregnancy rates and pregnancy loss. The primary aim of our study was to evaluate the prevalence of sperm DNA damage in younger and older men with normozoospermia. We obtained semen from 277 consecutive non-azoospermic men presenting for sperm DNA testing. The main outcome measures included sperm % DNA fragmentation index (%DFI, using sperm chromatin structure assay), sperm concentration, motility and morphology, and, paternal age. 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 (a parts per thousand yen40 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). 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.