Declining male fertility – an alarming trend
by Himanshu Sharma
Infertility is clinically defined by WHO as “a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse”. Infertility is classified into two forms. Primary infertility is the infertility in a couple who have never had a child. Secondary infertility is failure to conceive following a previous pregnancy. Infertility may be due to defect in any one of the partners. Male infertility refers to the inability of a male to achieve a pregnancy in a fertile female and it accounts for 40-50% of infertility cases .
Factors Responsible for Male Infertility
The most common causes of male infertility relate to the production and maturation of sperm. Sperm may be immature, abnormally shaped, or unable to swim properly. Normal sperm may be produced in abnormally low numbers (oligospermia) or seemingly not at all (azoospermia). These problems may be caused by many different conditions including:
- Infectious diseases or inflammatory conditions such as the mumps virus.
- Endocrine or hormonal disorders such as Kallman’s syndrome.
- Under certain conditions, the body starts producing inappropriate immune response against its own cells or tissues and destroy them. This condition sometimes may lead to infertility if immune response is stimulated against body own sperm cells and thus they are destroyed.
- Environmental and lifestyle factors.
- Genetic diseases (most are associated with sperm abnormalities, either directly or indirectly) such as cystic fibrosis, Noonan syndrome, myotonic dystrophy, Hemochromatosis, Kartagener’s syndrome (detailed information can be obtain from . Sex chromosomal abnormalities such Klinefelter syndrome, Turner syndrome or mutations in the gene responsible for spermatogenesis such as androgen receptor gene mutations or Y chromosomal microdeletion are also an important genetic factor responsible for male infertility.
- Defective delivery of sperm into the female genital tract which could be due to impotence or premature ejaculation.
Declining Male Fertility
A fall in the sperm count in the reproductive years is now a serious global problem [4,5]. A study shows that sperm count of healthy males is decreasing at a rate of 1-2% per year . This will directly affect population growth rate of any country, which in turn will affect the economic growth of a country. Declining male fertility can also cause mental dissatisfaction and disrupt relationships. The gradual decrease in sperm count in worldwide male population prompted WHO to revised its guideline recently by decreasing the sperm concentration range deemed as normal from 20 million/ml to 15 millions/ml in a healthy individual .
Aside from genetic and other idiopathic causes of male infertility, reports in recent years have shown that incidence of male infertility has increased as a result of various factors such as environmental pollution, stress and lifestyle . There are various contributing lifestyle factors responsible for declining sperm count. In this article, I will focus on major factors such as physiological stress, genital heat stress, smoking, and alcoholism.
Physiological Stress and Work Pressure
Physiological stress is one of the important factors contributing to male infertility. Studies have shown that in animals, social stress, high altitude, surgery, and immobilisation stress affect body weight, testosterone level, and copulatory behaviour with variable effects on testicular morphology . Evidence exists that mild-to-severe emotional stress decreases testosterone and interferes with spermatogenesis in the human male . It has been observed that some seminal antioxidant contents, as well as motility and morphologically normal spermatozoa, decrease in students undergoing examination stress . Antioxidants play a vital role in scavenging large amount of reactive oxygen species (ROS) produced in the body in response to smoking, drug and other environmental stresses. These ROS enhance lipid peroxidation in sperm cell, which could affect its motility and morphology. The presence of antioxidants in seminal fluid reduces ROS content and thus enhances reproductive capability .
Genital Heat Stress
Normal sperm production depends on an optimal testicular temperature which is maintained 2°C below body temperature, typically between 34 to 35°C . Seminiferous epithelium, where the maturation of sperm cell takes place is temperature sensitive. Moreover, enzyme activities involved in spermatogenesis will be affected at higher temperature. Therefore, an increase in the temperature of the scrotum sac affects spermatogenesis, and thus maturation of sperms. Prolonged sitting can lead to genital heat stress and consequently negatively affect semen quality. For example, the fertility parameters of professional drivers who spend long periods sitting in vehicles are reported to be impaired . Modern dress style in males such as wearing tight fitting underwear and jeans is also associated with significantly higher scrotal temperatures.
Cigarette smoke contains at least 400 toxic substances, which include arsenic, formaldehyde, and nicotine. The adverse effects of smoking such as its association with an increased risk of lung cancer, heart disease and oral cancer are often highlighted, yet the effect of smoking on infertility and sexual dysfunction is rarely mentioned. As a result, awareness about these additional ill effects of smoking is limited. Smoking not only affects sperm concentration, motility and morphology of sperms but it may also lead to erectile dysfunction and premature ejaculation, thus decreasing sexual performance and hence male infertility. Smoking is associated with raised levels of toxic chemicals such as lead and cadmium in the blood, and elevated levels of these chemicals have also been found in the semen of infertile smokers who had poorer semen parameters than nonsmokers; these toxic chemicals severely affect sperm quality. Notably, elevated level of ROS in semen of smoker is also the major cause of decreased semen quality in smokers (13). Penile erection requires large flow of blood and it should be retained in penile soft tissues to maintain erection. Smoking causes narrowing of blood vessels and thus decreasing the blood flow that leads to erectile dysfunction. Reports have also shown that smoking may also cause chromosomal abnormality thus affecting spermatogenesis .
It is a common misconception that alcohol consumption does not affect fertility in males. Alcoholism contributes either directly or indirectly to the decline in male infertility. In men, alcohol reduces testosterone levels by inhibiting its secretion by testis . A lack of testosterone leads to loss of libido and reductions in sperm quantity and quality. Alcohol consumption also affects sexual performance by decreasing libido and the ability to control ejaculation. Alcohol impairs nutrient absorption by damaging the stomach and intestinal cell lining and disabling transport of some nutrients into the blood . Absorption of zinc, an important mineral element involved in the formation of the sperm cells and maintaining its mobility, is drastically inhibited by alcohol consumption thus affecting both sperm quality and quantity .
Male infertility has profound psychological and social effects. Several evidences suggest that negative lifestyle can adversely affects male fertility. With the advancement of science, more infertile couples are opting for assisted reproductive technology; however these treatments are expensive and not accessible for all. Governmental and non-governmental organisations should increase their effort to highlight the adverse effects of certain modern lifestyle choices. Since lifestyle factor is by choice, it is vital to increase public awareness of the benefits of adopting healthy lifestyle to reduce the risk of infertility.
About the Author
Himanshu Sharma is a PhD student in the Department of Biochemistry Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The main focus of his research is on understanding the molecular basis of male infertility, specifically on the identification and molecular characterisation of mutations in CFTR gene from male infertility subjects in India. Recently, he has been awarded the Charpak PhD Fellowship 2012 by the French government for a six-month training at the University of Poitiers, France. He is also the recipient of the Indian Council of Medical Research (ICMR) Senior Research Fellowship in 2012. He can be contacted at [email protected] Find out more about Himanshu by visiting his Scientific Malaysian profile at http://www.scientificmalaysian.com/members/himanshu/.
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