Abnormal standard semen characteristics and reduced sperm chromatin maturity can appear with increasing male age. However, the influence of paternal age on semen parameters is still controversial. Therefore, this study was designed to estimate the influence of paternal age not only on conventional semen characteristics but also on sperm DNA integrity. This research was carried out on ejaculated sperm cells obtained from men (n = 1124) aged ≥40 y and <40 y. Our data revealed a decreased semen volume and an increased percentage of DFI (sperm DNA fragmentation index) in older men compared to younger men in the entire study cohort, in men with normozoospermia and in men with abnormal semen parameters. Moreover, there was a higher incidence of sperm DNA damage (>10% DFI, low fertility potential) in the groups of men aged ≥40 y than in the groups of men aged <40 y. Older men had over twice the odds ratio for high sperm DNA damage as younger men. Our findings suggest a detrimental effect of advanced paternal age on sperm chromatin integrity. The data show that the evaluation of sperm DNA has greater clinical utility than standard semen analysis in case of male fertility potential assessment.
Because the assessment of sperm DNA fragmentation (SDF) plays a key role in male fertility, our study was designed to find the relationships between SDF and standard semen parameters. The receiver operating characteristic (ROC) curve showed that 18% SDF is a prognostic parameter for discriminating between men with normal and abnormal standard semen parameters (n = 667). Men with > 18% SDF had significantly lower quality semen, a higher prevalence of abnormal semen characteristics, and a higher odds ratio for abnormal semen parameters compared to men with ≤ 18% SDF. An ROC analysis provided predictive values for age and semen parameters to distinguish between men with SDF > 18% and men with ≤ 18% SDF. SDF was positively correlated with male age and teratozoospermia index but negatively with sperm concentration, total number of spermatozoa, sperm morphology, progressive motility, and vitality. Our study shows that 18% SDF has a predictive value for distinguishing between men with normal and abnormal semen characteristics. Men with >18% SDF have a higher risk for abnormal semen parameters, while age and obtained semen parameters have a predictive value for SDF. There is a relationship between SDF and conventional sperm characteristics, and thus, SDF can be incorporated into male fertility assessment.
Background: The pathogenesis of teratozoospermia (<4% morphologically normal sperm cells) and the relationship between sperm morphological abnormalities and abnormal sperm nuclear DNA fragmentation, which are considered indicators of male fertility, have not been elucidated. Our research was designed to determine the prevalence of different sperm DNA fragmentation (SDF) levels in men with teratozoospermia and to establish a discriminating threshold value for SDF in assessing sperm morphology.Methods: Basic semen characteristics and detailed sperm morphological analysis (head, neck, midpiece, and tail defects and excess residual cytoplasm) (WHO, 2010), and the nuclear sperm DNA dispersion test were performed on semen samples obtained from 523 men with teratozoospermia (n=296) and those without teratozoospermia (n=227).Results: Subjects with abnormal sperm morphology had not only lower results for standard sperm characteristics, including detailed sperm morphological abnormalities, but also a higher proportion of sperm cells with SDF vs. men with normal sperm morphology. Moreover, significantly fewer subjects with low SDF levels (≤15%), more subjects with high SDF levels (>30%) and a higher odds ratio (OR) for having high SDF levels were found in the group of men with teratozoospermia vs. men without teratozoospermia. However, the receiving operating characteristic (ROC) curve analysis indicated that a SDF >18% was a significant negative predictive value to distinguish between men with normal sperm morphology or men with abnormal sperm morphology. The optimal area under the ROC curve (AUC) was 0.746. In the group of men with teratozoospermia, a higher incidence of men with >18% SDF and a higher OR for having >18% SDF were observed. SDF negatively correlated with sperm number, morphologically normal sperm cells, sperm motility and sperm vitality but positively correlated with the teratozoospermia index (TZI) and detailed sperm morphological abnormalities. Conclusions:The obtained findings demonstrated that: (I) detailed sperm structural defects coexist with abnormal nuclear sperm DNA dispersion, (II) men with teratozoospermia may have a higher risk for sperm DNA damage, (III) the calculated optimal SDF value of 18% measured by the DNA sperm dispersion test is the best criterion to predict normal and abnormal sperm morphology.
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