Effects of diabetes mellitus on sperm quality and fertility outcomes: Clinical evidence

BackgroundDiabetes mellitus is a global epidemic characterized by high morbidity and mortality. Diabetes mellitus can lead to acute and chronic systemic complications. Among them, a negative effect of diabetes mellitus on sperm quality and male/couple fertility has been suggested. However, available studies in diabetes mellitus men evaluated relatively small cohorts with discordant results. ObjectivesTo evaluate the clinical evidences of the effects of diabetes mellitus on sperm quality and fertility outcomes. MethodsAn extensive Medline search was performed identifying studies in the English language. ResultsThe prevalence of diabetes mellitus in infertile men ranges from 0.7% to 1.4%, while the prevalence of infertility in diabetes mellitus men, evaluated in a few studies, ranges from 35% to 51%. Male diabetes mellitus seems to play a negative effect on couple fecundity, while being childless or subfertile men might increase the risk of diabetes mellitus. Available cross-sectional studies investigating semen parameters and male sexual hormones in men with diabetes mellitus are heterogeneous, assessed relatively small cohorts, show often discordant results and frequently are not directly comparable to derive robust conclusions. Two meta-analyses support a negative effect of diabetes mellitus on sperm normal morphology and no effect on sperm total count, with contradictory results regarding other semen parameters. Considering only studies on type 1 diabetes mellitus men, meta-analyses support a negative effect of diabetes mellitus on sperm motility and no effect on sperm total count, with contradictory results regarding other semen parameters. The rate of children observed among type 1 diabetes mellitus men was lower than controls, especially in subjects with a longer diabetes mellitus duration. Couples with a diabetes mellitus male partner undergoing assisted reproduction techniques showed lower pregnancy rates than controls. No study evaluated the impact of diabetes mellitus treatment on semen quality and male fertility. ConclusionsOverall, available data show that diabetes mellitus might impair male reproductive health and couple fertility. However, further larger and full of details studies are needed.