Association between serum Vitamin D levels and sperm DNA fragmentation index in varicocele patients: a retrospective cohort study.

OBJECTIVE

While varicocele is a major cause of male infertility, the role of vitamin D in sperm DNA integrity remains unclear. This study aimed to investigate the association between serum vitamin D levels and sperm DNA fragmentation index (DFI) in varicocele patients.

METHODS

This retrospective cohort study conducted at Fujian Maternity and Child Health Hospital included 355 varicocele patients aged 18-45 years (June 2021-June 2024). The primary exposure was serum 25-hydroxyvitamin D level, and the primary outcome was DFI. Multiple linear regression models were used to analyze the association between vitamin D and DFI, adjusting for age, BMI, smoking, alcohol consumption, and other confounders.

RESULTS

A significant inverse association was found between vitamin D levels and DFI (β = -0.24, 95% CI: -0.28 to -0.19, P < 0.0001). Piecewise linear regression identified a threshold at 25.9 nmol/L, below which the inverse association was more pronounced (β = -1.0, 95% CI: -1.2 to -0.8, P < 0.001).

CONCLUSION

Serum vitamin D levels have been demonstrated to be significantly associated with the rate of sperm DNA fragmentation index in patients with varicocele, particularly at levels below 25.9 nmol/l.