Involvement of Oxidative Stress in Decreased Number and Motility of Sperm in Men without Obvious Causes for Male Infertility

Background: Male factors contribute to approximately 50% of infertile couples. However, obvious causes remain unknown in many cases. This observational study aimed to investigate the associations of clinical and lifestyle parameters with sperm parameters. Materials and Methods: This study enrolled 41 men of infertile couples without obvious causes for male infertility from July 2023 to April 2024. Semen samples were evaluated for sperm number, motility, DNA fragmentation, and oxidative stress (OS) marker oxidation-reduction potential (ORP). Blood samples were analyzed for biochemical parameters, including advanced glycation end products (AGEs) and systemic OS marker diacron-reactive oxygen metabolites (d-ROMs). Skin-accumulated AGEs levels were identified with an autofluorescence method. Lifestyle factors were assessed with a lifestyle questionnaire. Results: Most of the participants were under 40 years old and non-obese with normal clinical and sperm parameters. Multiple regression analyses revealed that body mass index, serum d-ROMs, and semen ORP levels were independently associated with decreased sperm number. Additionally, serum zinc and semen ORP levels were associated with sperm motility. Furthermore, serum zinc and high-density lipoprotein-cholesterol levels were associated with sperm progressive motility and DNA fragmentation, respectively. The rest of the clinical and lifestyle factors, including skin-accumulated and serum AGE levels were not correlated with any sperm parameters. Furthermore, serum d-ROMs and semen ORP levels were not correlated with each other or any of the clinical and lifestyle factors. Conclusions: Our present study indicates that both systemic and local OS may be independently involved in sperm abnormality of healthy men without obvious causes for male infertility.