Introduction, Incidence & Prevalence of Male Infertility
Male infertility refers to a male’s inability to ‘create’ a pregnancy in a fertile female. “Male factor” infertility is seen as an alteration in sperm concentration and/or motility and/or morphology in at least one sample of two sperm analysis collected 1 and 4 weeks apart. In humans, it accounts for 40-50% of infertility and affects approximately 7% of all men.
Is male infertility on the rise?
Analysis of retrospective data indicates that sperm counts may have declined in some parts of the world, but there seem to be geographical variations in the semen quality. Male infertility in India has been increasing steadily over the last decade and it has reached a state where it is considered alarming.
As early as in the 1980s, many scientists/clinicians reported an emerging concern about deteriorating semen quality. In 2000, an updated comprehensive meta-analysis was done, which also confirmed the falling trend in sperm count. Also, another meta-analysis reported that sperm density has decreased globally by about 50% over the past 50–60 years.
Trends of male infertility in India.
Doctors from the All India Institute of Medical Sciences (AIMS) reported that over 12–18 million couples in India are diagnosed with infertility every year. They have reported that while the sperm count of a normal Indian adult male used to be 60 million/ml three decades ago, it now stands at around 20 million/ml.
It was found that majority of men who were exposed to high temperature at their workplace – welders, dyers, blast furnace workers and those employed in cement and steel factories – were more prone to infertility. This is due to excess environmental heat which increases the temperature of the scrotum, causing a negative effect on sperm production. A 1° elevation in testicular temperature leads to 14% depression of spermatogenesis. Not only has quantity of sperm production declined in males across the world, but there has also been a decrease in motility and morphology of the sperms.
There has been a 2% decrease in quality of male sperm annually. About 40% men in the reproductive age group are presently recording a quantitative and qualitative decline in sperm quality. According to a 10-year comparison study on sperm quality and quantity (2000–2001 to 2010–2011), the percentage of semen ejaculation, which is considered less than normal (below 4 ml), increased from 34% to 65% and the most suitable ejaculation volume (more than 4 ml) went down from 15% to 3%.
As far as the morphology of sperm was concerned, in 2000–2001, 26% of the sperms showed above 60% normality, whereas in 2000–2011 this was reduced to 7%. However, a similar study in Calcutta, which included semen analysis of 3729 men presenting with infertility problems in two distinct decades, that is, between 1981–1985 and 2000–2006 concluded a significant decline in the sperm motility parameters and seminal volume in the present decade, but no change in overall sperm concentration. A decline was seen in sperm motility with increasing age in both decades.
Causes for the Increase in Male Infertility
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. Aging is an important factor responsible for the decline in semen quality, as first described in 1969 by Sasano and Ichijo, that the sperm concentration decreases as men age. They reported that 90% of seminiferous tubules in men in their 20s and 30s contained spermatids, whereas men in their 40s and 50s had spermatids in 50% of their seminiferous tubules. Only 10% of seminiferous tubules from men aged >80 years contained spermatids.
In contrast to concentration, evidence consistently indicates that sperm motility decreases with advancing age. Various studies revealed statistically significant decreases in motility of 0.17–0.6% per year of age resulting in a 3–12% decline in motility over 20 years. Similar to motility, morphology appears to decrease with advancing male age. Studies indicate a decline in normal sperm morphology of 0.2–0.9% per year of age, resulting in a 4–18% decrease in normal morphology over a 20-year period.
Male infertility is increasing significantly and now contributes to about 40% of all infertility cases. The key reasons for this increase have not been identified, but experts think it is due to life style changes (smoking, alcohol, substace abuse, stress, lack of physical activity, diet etc.), working conditions and age.