Causes and Risk Factors for Male Infertility: A Scoping Review of Published Studies

Background: Despite the evidence of declining sperm counts worldwide and the increasing prevalence of male infertility, there has been limited documentation of the potential causes and risk factors for male infertility. With limited methods of primary treatment of male infertility, understanding the causes and risk factors will pinpoint specific lines of prevention. Objective: We reviewed published studies on causes and risk factors for male infertility and identify gaps in the literature enabling more focused research and innovations. Design/Setting: The study was a scoping review. The review included studies on the causes and risk factors of male infertility published in scientific/academic publications. It was not limited to any region or date. The following databases were searched: Cumulative Index to Nursing and Allied Health Literature, Wiley online, HINARI, Science Direct, PubMed/Medline, Google Scholar, African Journals Online, and the WHO Repository. In total, 1295 articles were identified. After removing 357 duplicates, 938 articles were screened, and 71 articles were identified for inclusion, while 60 articles met the inclusion criteria. Results: Four broad causes and risk factors of male infertility identified were 1) biological/physiological/genetic causes, 2) behavioral/lifestyle risk factors, 3) environmental factors, and 4) socio-demographic risk factors. However, no substantive results on actual causes under each category were identified, leaving gaps for further research and experimentation. Conclusion: The results indicate limited knowledge of the actual causes of male infertility in published studies. The gaps in knowledge that need to be bridged to enable a fuller understanding of the actual causes of male infertility were highlighted. Keywords: male infertility, causes, risk factors, scoping review, spermatozoa defects