OBJECTIVE: The purpose of this study was to determine statistical correlations of age of men with potential male factor infertility and SCSA measures of sperm DNA fragmentation (DFI) and High DNA Stainable Sperm (HDS) in 25K clinical semen samples.
DESIGN: 25K semen samples sent from infertility clinics and individuals signing consent forms from January 2007 to November 2017 were measured by the SCSA test. These data were statistically analyzed for determining effects of age on sperm DNA integrity.
MATERIALS AND METHODS: Following liquefaction, aliquots of semen were transferred to cryotubes, flash frozen in LN2 and shipped to SCSA Diagnostics, Inc. in LN2 shippers or dry ice boxes by Federal Express Inc. Individual thawed samples were independently measured twice by the SCSA test protocol. The raw data were processed through SCSAsoft software to produce a clinical report.
RESULTS: : In brief, at ages 20-25, 40-45, 60-65, the mean [min, max] for DFI, SD DFI and HDS were are shown in Fig. 1. The percent of men with mean %DFI > 20%, 25% and 50% is 30%, 20%, and 3%, respectively. An estimate for the change point in slope of age vs. %DFI is age 41.6 with a 95% confidence interval of (40.4, 42.8). The slope before age 41.6 was estimated to be 0.39 and after age 41.6 was 0.86. An estimate for the change point in slope of age vs. SD DFI was age 40.0 with a 95% confidence interval of (36.7, 43.0). The slope before age 40.0 was estimated to be 1.51 and after age 40.0 was 2.22. According to logistic regression model, the estimated probability that the mean DFI >20% for ages 20, 25, 30, 35, 40, 45 and 50 were 0.10, 0.13, 0.18, 0.245, 0.33. 0.42 and 0.52 respectively; e.g., a 40-year-old man has a 1/3 mean chance to have >20% DFI by age factor alone. From loess smooth, the relationship of %HDS with age is observed to be linear with an estimated slope of -0.137 (SE = 0.0062).
CONCLUSIONS: These SCSA test data clearly show a strong relationship between age of men attending an infertility clinic and sperm DNA fragmentation. Previous studies suggest that the SCSA test has three clinical thresholds for %DFI: 1) >20% DFI (30% of men at this level) for beginning of loss of fertility potential, especially if one or more classical semen parameters are present, 2) >25% DFI (20% of men) for natural and IUI fertilization, and 3) >40% DFI for low probability of success for IVF/ICSI fertilization. Idiopathic couples, especially those above age 41.6, as shown here, even with the man having all normal semen parameters, would be strongly advised to determine their SCSA test values and seek counsel as to a plan that increased chance of pregnancy.