The relationship between age and DNA fragmentation index: Use of sperm chromatin dispersion assay to evaluate the sperm DNA fragmentation

Abstract

Objective: To evaluate sperm DNA fragmentation using the sperm chromatin dispersion (SCD) assay in a large retrospective cohort and to assess age-related patterns of DNA damage. Methods: This retrospective observational study included 456 semen samples obtained from male partners of infertile couples. Sperm DNA fragmentation was assessed using the SCD method, and the DNA fragmentation index (DFI) was calculated as the percentage of spermatozoa showing the absence of halo formation and degraded nuclei. Participants were stratified into four age groups (≤30, 31–35, 36–40, and >40 years). Mean DFI values and the prevalence of abnormal DFI (≥25% and ≥30%) were analyzed across the age groups. Results: Mean DFI values did not differ significantly among age groups (p=0.637). Correlation analysis showed a weak, non-significant association between age and DFI. However, the proportion of samples with abnormal DFI (≥25%) increased progressively with age, reaching 55.4% in men older than 40 years. A similar trend was observed for severe DNA fragmentation (DFI ≥30%). Conclusion: Although mean DFI values were comparable across different age groups, advancing age was associated with a higher prevalence of clinically significant sperm DNA fragmentation. These findings support threshold-based interpretation of DFI and highlight the clinical utility of SCD testing in routine male infertility evaluation, particularly in older individuals.