Which isolated sperm abnormality is most related to sperm DNA damage in men presenting for infertility evaluation

Sperm DNA damage is common in infertile men and is associated with poor semen parameters but the impact of an isolated sperm abnormality on sperm DNA damage has not been studied. To evaluate sperm DNA damage in a large cohort of infertile men with isolated sperm defects. Retrospective study of 1084 consecutive, non-azoospermic infertile men with an isolated sperm defect: isolated oligozoospermia (iOligo), isolated asthenozoospermia (iAstheno) or isolated teratozoospermia (iTerato). We examined and compared clinical parameters, conventional semen parameters and %sperm DNA fragmentation (%SDF, assessed by flow cytometry-based Terminal deoxynucleotidyl transferase-mediated dUTP Nick End-Labeling assay) in the three groups of men. The mean (+/- SD) %SDF was significantly higher in the iAstheno compared to the iOligo and iTerato groups (25.0 +/- 14.0 vs. 19.2 +/- 11.6 and 20.7 +/- 12.1 %, respectively, P < 0.0001). Similarly, the proportion of men with high %SDF (> 30 %) was significantly higher in the iAstheno compared to the iOligo and iTerato groups (31 % vs. 18 % and 19 %, respectively, P < 0.0001). In the group of 713 men with iAstheno, %SDF was positively correlated with paternal age (r = 0.20, P < 0.0001) and inversely correlated with %progressive motility (r = -0.18, P < 0.0001). In the subset of 218 men with iTerato, %SDF was also positively correlated with paternal age (r = 0.15, P = 0.018) and inversely correlated with %progressive motility (r = -0.26, P = 0.0001). In this large cohort of infertile men with isolated sperm abnormalities, we have found that the sperm DNA fragmentation level is highest in the men with sperm motility defects and that 31 % of these men have high levels of sperm DNA fragmentation. The data indicate that poor motility is the sperm parameter abnormality most closely related to sperm DNA damage.