Of all infertility cases, approximately 40–50% is due to “male factor” infertility and as many as 2% of all men exhibit suboptimal sperm parameters.The fertility rate in men younger than age 30 years has decreased worldwide by 15%. The rates of infertility in less industrialised nations are markedly higher and infectious diseases are responsible for a greater proportion of infertility.
The decline in the semen quality coincides with an increasing incidence of abnormalities of the male genital tract including testicular cancer and cryptorchidism in various countries.
Sperm density has decreased globally by about 50% over the past 50–60 years with 2% decrease in quality of male sperm annually.
The exact reason for the decline in semen quality is not clear, but it may be due to environmental, nutritional, socioeconomic or other unknown causes.