In this research, scientists in Japan looked at sperm DNA in infertile and fertile men to see how damaged it was. They used a special test called the sperm DNA fragmentation index (DFI) to measure this damage. The study included 743 infertile and 20 fertile men. They found that a DFI value above 24% was linked to infertility. Fertile men had lower DFI (around 7.7%) compared to infertile men (around 19.4%). Sperm quality like concentration, motility, and shape was worse in men with higher DFI. This test can reveal sperm problems not shown in standard semen tests, helping understand male fertility issues better. If a man has high DFI, it might impact his chances of fathering a child through natural or assisted methods.