Background: The aim of our study was to evaluate the quality of semen of a large sample from general healthy population living in Italy, in order to identify possible variables that could influence several parameters of spermiogram.
Methods: We conducted a cross-sectional study from February 2010 to March 2015, collecting semen samples from the general population. Semen analysis was performed according to the WHO guidelines. The collected data were inserted in a database and processed using the software Stata 12. The Mann-Whitney Test was used to assess the relationship of dichotomus variables with the parameters of the spermiogram; Kruskal-Wallis Test for variables with more than two categories. We used also Robust regression and Spearman correlation to analyze the relationship between age and the parameters.
Results: We collected 5680 samples of semen. The mean age of our patients was 41.4 years old. Mann-Whitney Test showed that the citizenship (codified as "Italian/Foreign") influences some parameters: pH, vitality, number of spermatozoa, sperm concentration, with worse results for the Italian group. Kruskal-Wallis Test showed that the single nationality influences pH, volume, sperm motility A-B-C-D, vitality, morphology, number of spermatozoa, sperm concentration. Robust regression showed a relationship between age and several parameters: volume (P=0.04, R2=0.0007 β: -0.06); sperm motility A (P<0.01; R2=0.0051; β=0.02); sperm motility B (P<0.01; R2=0.02; β=-0.35); sperm motility C (P<0.01; R2=0.01; β=0.12); sperm motility D (P<0.01; R2=0.006; β=0.2); vitality (P<0.01; R2=0.01; β=-0.32); sperm concentration (P=0.01; R2=0.001; β=0.19).
Conclusions: Our patients had spermiogram's results quite better than the standard guidelines. Our study showed that the country of origin could be a factor influencing several parameters of the spermiogram in healthy population and through robust regression confirmed a strict correlation between age and these parameters.