Using the DFI evaluation for semen tests enabled clarification of the correlation between DFI and various factors that are considered to be related to the performance outcome of assisted reproductive technologies.
There are still many unknown aspects of the causes of infertility that are related to male factors rather than female factors. Generally, semen tests used for evaluation and diagnostics focus primarily on semen fluid volume, sperm concentration, motility, and malformation rate.
The information obtained in these general semen test findings are considered inadequate for determining sperm potential. To more accurately evaluate the correlation between IVF clinical outcomes and male infertility, we focused on DFI measurements.
DFI is a method for detecting the integrity of sperm nuclear DNA and the extent of damage. DFI is reported to increase with age in men. Reports have shown that close to 8% of infertile men have high DFI values ( ≧ 30%) (12). Reports have also suggested that factors associated with sperm DNA damage are affected by abnormal sperm lipids, reproductive hormones, and mitochondria (13). These factors are involved in oxidative stress and apoptosis formation due to an age-dependent decline in male fecundity. Therefore, causing an age-related increase in DNA damage (14).
The results of our DFI measurements in this study showed that DFI tended to increase with age, as described in previous reports (15–17). However, DFI is not only affected by age, but also by indulgences such as cigarettes (18) and alcohol (19), lifestyle habits such as sleep and exercise, and intake of supplements (20). Thus, various aspects of aging, multiple stress factors, and negative factors affecting the DFI require further investigations (21). In terms of the link with IVF outcomes, it has been reported that, although there is no difference in the fertilization rate and embryonic development rate between high DFI and low DFI (22), a high DFI tends to be associated with higher rates of miscarriage, resulting in a low live birth rate per transplantation (23, 24). The patients who underwent DFI analysis in this study provided semen samples before IVF treatment. The mean DFI was 15.6 ± 11.5%. Generally, DFI levels of ≥ 30% are considered to be high, and therefore, it is necessary to investigate the correlation between elevated DFI and IVF outcomes.
We also found that DFI was significantly lower in the group below the criteria compared to the group at or above the criteria for sperm concentration, motility, and normal morphology, in semen tests conducted in accordance with the WHO criteria (25). The results suggest that, when the WHO criteria test results were good, DFI evaluation was also generally good (26). However, it is necessary to suspect damage to the sperm nucleus when IVF outcomes are poor despite patients satisfying the WHO criteria, and DFI analysis may be useful as an additional semen test in these circumstances.