VITAMIN D AND SPERM DNA FRAGMENTATION AND SEMEN QUALITY IN AN INFERTILITY TREATMENT-SEEKING POPULATION.

Vitamin D receptors and metabolizing enzymes are expressed in the testis and prostate and have been shown to impact the male androgenic hormone axis. Vitamin D is hypothesized to play a key role in male reproduction through these mechanisms, though reported associations between vitamin D levels and sperm DNA fragmentation and semen quality are inconsistent. In a longitudinal study of men (n=2369) seeking infertility care, serum 25(OH)D was measured at baseline and semen quality was assessed using standardized procedures by quantification of sperm concentration, volume, motility, morphology, count, and total motile count at baseline and 6-months post-enrollment and with DNA fragmentation at 6-months assessed using both COMET and SCSA. The data were analyzed using weighted linear regression adjusted for age, body mass index, race, season at enrollment, abstinence time, income, and multivitamin use. Models were weighted to account for participants who did not contribute a semen sample at the 6 month follow-up visit. Vitamin D status was assessed continuously and categorized as deficient (<20 ng/mL, reference), insufficient (20-29.9 ng/mL), or sufficient (≥30 ng/mL). Overall, 29% of men had deficient levels of 25(OH)D at baseline, 41% were insufficient, and 30% were sufficient. 25(OH)D status was not associated with semen quality parameters assessed at baseline. Sufficient 25(OH)D was also not associated with semen quality parameters at 6-months post-enrollment (total motile count <20 million: RR 1.01, 95% CI 0.68, 1.48 sufficient vs deficient; RR 1.25, 95% CI 0.90, 1.74 insufficient vs deficient; morphology <4% normal: RR 0.93, 95% CI 0.74, 1.17 sufficient vs deficient; RR 0.84, 95% CI 0.69, 1.04 insufficient vs deficient; count ≤39 million: RR 0.83, 95% CI 0.55, 1.25 sufficient vs deficient; RR 0.96, 95% CI 0.67, 1.26 insufficient vs deficient; motility ≤40% motility: RR 1.06, 95% CI 0.77, 1.47 sufficient vs deficient; RR 1.07, 95% CI 0.80, 1.44 insufficient vs deficient). No associations were observed with sperm DNA fragmentation assessed using COMET (β=0.1, 95% CI: -3.8, 3.9 sufficient vs deficient; β=1.6, 95% CI: -1.6, 4.7 insufficient vs deficient) or using SCSA (β=-0.4, 95% CI: -3.3, 2.6 sufficient vs deficient; β=0.7, 95% CI: -1.8, 3.2 insufficient vs deficient). Similar results were observed in continuous models. 25(OH)D levels were not associated with sperm DNA fragmentation or traditional semen quality parameters in a cohort of men seeking infertility care who underwent multiple, standardized assessments of semen quality. Future research should investigate whether 25(OH)D in the male partner is related to pregnancy and its outcomes, irrespective of semen quality metrics.