By Dr. Colin Michie FRCPCH University of Central Lancashire.
Infertility for a man means he cannot achieve conception in a year of unprotected intercourse with a fertile woman. Around one in six of adults globally suffer with this problem. Reviews suggest the quality of human semen across populations of many countries has deteriorated over the last fifty years. Similar trends have been observed in semen analysis for dogs and horses.
This challenges men with an important signal relating to their health, to male “virility.” It may stigmatise our roles in our communities. New measures of sperm quality, along with novel tests to examine sperm formation in the testes are improving clinical knowledge. Human testes normally manufacture 2-300 million sperm a day. They are processed over 2-3 months: only half reach final maturity. This complex process is carefully regulated by several hormones, the temperature in the testicles, controls of oxidative damage and protection in the semen. The lifestyle of the owner of those testicles is important too!
Sperm quality is optimal in the second decade of life; spermatozoa show signs of deterioration after this. For instance, in a 12 month test, it is 30% less likely that a man over 40 can conceive than one under 30. With age semen volume, the numbers of sperm, their ability to swim well (their motility) and their shape all decline. Exceptionally, some can father a child when over 90. However sperm from older men have been exposed to environmental assaults for longer; they may accumulate damage in their genetic material that influences their children.
Children whose fathers are in their late 50s have a greater chance of being born prematurely, small and requiring assistance following birth. They have more learning problems in school and have a higher risk of suffering with childhood cancers. Mental health issues including autism may be more frequent too. Some have proposed that it might be wise for prospective fathers to be counselled about these risks, and for younger men to consider perhaps banking their sperm.
Apart from age, what reasons are there for men to be infertile? Experiences from clinics suggest that exact causes cannot always be found in individuals. Some 7% of men cannot father children because of inherited genetic reasons, surgery, trauma, cancers or drugs used to treat other diseases which have damaged the testicles. A number may suffer from erectile dysfunction or problems with ejaculation. Alcohol and androgenic steroids contribute too, as does the use of tobacco and marijuana. Infections of the male genital tract by mumps, zika, hepatitis B and West Nile virus can cause damage sperm protection within the testis; HIV and HTLV-1 will have similar effects. These viruses can persist in the testes, several are spread readily in semen. Some genital infections such as syphilis or gonococcus can be more destructive by causing tissue damage that then reduces fertility.
In small numbers of men an undiagnosed problem with coeliac disease can impair fertility. This condition is an autoimmune disease caused by a sensitivity to gluten, a protein found in wheat, rye and barley. Typically coeliac will have caused gut problems in younger sufferers, but diagnoses can be delayed. Fertility can be restored in most of those with coeliac disease by removing gluten from their diets – a relatively simple solution! In others a structural problem such as a varicocele in the testes – a varicose vein – can increase the temperature in the testicles, which prevents effective sperm production. These may be corrected with surgery.
This diverse list does not account for the progressive recent deterioration in sperm quality in humans and other animals. Environmental changes of many types are a probable explanation. However in man it is likely that obesity and related type 2 diabetes in particular prevent the manufacture of successful sperm. Sperm samples from men with a BMI over 30 are less successful in artificial insemination procedures.
Treatments are evolving rapidly to improve live birth rates. Increased physical activities reverse many negative influences. For some, specific hormonal treatments are required. A Mediterranean diet improves sperm quality by improving antioxidant levels. Complementary botanical approaches range from using saffron, black cumin and ashwagandha to sesame or the locust bean. More trials are needed in order to find out their various optimal dosing. From a surgical perspective, in well-provided health care systems, sperm can be used to artificially fertilise an egg for implantation using intracytoplasmic sperm injection.
Spermatozoa, those epic and silent swimmers, are the smallest human cells. Their contribution to the amazing process of conception is central to our cultures. When conception is challenging, clinical expertise may become crucial. Establishing these services is a priority for couples in all communities. A One Health approach is needed too as we are not the only species affected and all the underlying causes need to be found.
Useful resources:
https://www.nhs.uk/conditions/infertility/causes/
https://www.who.int/news/item/04-04-2023-1-in-6-people-globally-affected-by-infertility
Dr. Colin Michie is currently the Associate Dean for Research and Knowledge Exchange at the School of Medicine in the University of Central Lancashire. He specializes in paediatrics, nutrition, and immunology. Michie has worked in the UK, southern Africa and Ghaza as a paediatrician and educator and was the associate Academic Dean for the American University of the Caribbean Medical School in St. Maarten a few years ago.
