Research into reproductive biology is one of the most fascinating corners of medicine and science; my interest in this field was one of the driving forces behind my decision to go to medical school. Work in this field has resulted in life-changing treatments for infertile patients. More than one million babies have been born in the US to otherwise infertile couples, thanks to lab-assisted techniques like in-vitro fertilization (IVF).
At the same time; there remains a massive amount of research to do. Treatments for women whose number of eggs are prematurely low (diminished ovarian reserve), understanding of the causes and treatments of low or zero sperm counts (azoospermia) in male patients, non-surgical male contraception — all of these topics are incompletely understood at present. As a result, infertile patients continue to suffer.
A recent study (Levine et al., Human Reproduction, 2017) draws attention to this knowledge deficit; the study authors reviewed the entire body of existing research on male sperm counts published between 1973 and 2011. Their analysis reveals a startling trend: throughout the Western world, in both fertile men and infertile men seeking treatment, sperm counts dropped by almost 50% across these four decades.
This new study raises obvious questions: why might this decrease be occurring? Is this trend indicative of other ongoing changes in men’s health? Are there obvious causes of this trend and can they be acted upon? As a researcher in this field, I know the importance of answering that last question — what might be the causes and what do we do about them — and I know that there is already ongoing research on this front. But certainly more is needed.
Possible explanations include lifestyle factors (increasing obesity, tobacco use and its lingering effects), aging demographics of people pursing family building, environmental exposures to substances including plastics, hormones, radiation and radio frequency networks, and biological changes — the results of what we call epigenetic change — from fertility or hormonal treatments. Several factors could potentially be at play at the same time.
Unfortunately, obtaining an answer to this conundrum is challenging at best. There are unique barriers to answering these questions through experiments (including the obvious fact that experiments to prove these theories cannot be performed in humans). Even if we had an answer as to a single culprit, the further question of “What can we do about it?” seems even more daunting.
That being said, I remind people whenever I can that no field of research is more important than understanding the biology of conception. Cancer research, cardiovascular health research — these fields will enable us to live longer. But, of course, that ceases to be important if a hypothetical fertility crisis results in fewer or even no babies being born. Understanding human fertility is a vital part of understanding the cycle of human life and death.
Interestingly, our fertility research is governed by the American Society of Reproductive Medicine, whose first national meeting was held almost 75 years ago. I often point out that the meeting topics on male fertility at that first meeting are still being discussed at our current meetings. The need for further research in our field was already urgent. Dr. Levine’s study makes that need even more vital.
I am asked repeatedly what I tell my patients about this study. I remind people that healthy behavior is the easiest intervention patients can opt into. Studies have found that smoking cessation, sleep hygiene, and diet promote healthy sperm count. That being said, we will continue to test for potential causes of male fertility and we will act upon the causes that are correctable.
I know that this recommendation constitutes basic common sense, and it is the advice that I would give to a friend or a family member. But in the back of my mind, every time I am saying this to someone, I am asking myself the question of how we can do more or be better. What further research study will help us to better understand both the worldwide trends in fertility and problems each of my individual patients face? Hopefully the conversation this study has started will enable that research to become a reality.
