Umbrella review identifies risk factors and protective factors for male infertility and semen quality

Male infertility poses a substantial healthcare challenge and severely impacts the lives of patients. We aimed to investigate the risk factors for infertility and abnormal semen parameters. We conducted a comprehensive search of the articles published in Web of Science, MEDLINE, and Embase databases from January 2000 to February 2025. Infertility, semen volume, sperm concentration, sperm count, sperm morphology, sperm motility, and sperm progressive motility were used as endpoints to evaluate the relevance of risk factors. A total of 43 studies were included, covering 67 risk factors associated with infertility and abnormal sperm parameters. A total of 249 effect sizes were scored individually using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool, of which 136 (54.6%) were classified as "very low", 59 (23.7%) as "low", and 54 (21.7%) as "moderate". Suffering from type 1 diabetes, metabolic syndrome, hyperthyroidism, systemic lupus erythematosus, chronic prostatitis, and leukocytospermia may increase the risk of abnormal semen parameters. Poor lifestyle habits (obesity, sleep disorders, and smoking), exposure to pollutants and various compounds (carbon disulfide, organophosphates, and lead), the use of medications (sulfasalazine, mesalazine, and selective serotonin reuptake inhibitors), and even some viral infections (severe acute respiratory syndrome coronavirus 2, human papillomavirus, and hepatitis viruses) were associated with decreased semen quality. Regular physical exercise, nut consumption, and adherence to a healthy dietary pattern may reverse this process. An increasing number of factors are associated with infertility; however, some of the aforementioned studies lack verification of causal relationships. Future studies need to be well designed to further confirm these relationships.