Another day, another slew of articles full of fear mongering. This one is on sperm decline in the West. Is it true? I have recently covered on this blog that as of July 17th, 2017, the testosterone range for men decreased (more on that when I get access to the paper). I have also covered the obesity epidemic a bit, and that also factors in to lowered testosterone and, of course, low spermatoza count. Due to these environmental factors, we can logically deduce that sperm counts have fallen as well. However, as I will cover, it may not be so cut and dry due to analyzing numerous studies with different counting methodologies among numerous other confounds that will be addressed below. First I will cover the physiology of sperm production and what may cause decreases in production. Next, I will cover the new study that is being passed around. Finally, I will talk about why you should worry about this.
Physiology of sperm production
The accumulation of testosterone by ABP leads to the onset and rising rate of sperm production. So if testosterone production ceases or decreases, then subsequent decreases in sperm count and spermatogenesis should follow. If this change is drastic, infertility will soon follow. The process of sperm production is called spermatogenesis. It occurs in the seminiforous tubules and involves three main events: 1) remodeling relatively large germ cells into smaller mobile cells with flagella, 2) reducing the chromosome number by half, and 3) shuffling the genes so that each chromosome in the sperm carries novel gene combinations that differ from the parents. This is what ensures that a child will differ from their parents but still, at the same time, will be similar to them. The process by which this occurs is called meiosis, in which four daughter cells split which subsequently differentiate sperm (Saladin, 2010: 1063).
After the conclusion of meiosis I, each chromosome is still double stranded, except each daughter cell only has 23 chromosomes becoming a haploid while at the end of meiosis II, there are four haploid cells with 23 single-stranded chromosomes. Fertilization then combined the 23 chromosomes from the father and mother, which “reestablishes the diploid number of 46 chromosomes in the zygote“(Saladin, 2010: 1063-1064).
Spermatogonia divide by mitosis and then enlarge to become primary spermatocyte. The cell is then protected from the immune system since it is going to become genetically different from the rest of the cells in the body. Since the cells are guarded from the body’s immune system, the main spermatocyte undergoes meiosis I, giving rise to equal size haploid and genetically unique secondary spermatocytes. Then, each secondary spermatocyte undergoes meiosis II dividing into two spermatids with a total of four spermatogoniom. Lastly, the spermatozoa undergo no further division but undergoes spermiogenesis in which it differentiates into a single spermatozoon (Saladin, 2010: 1065-1066). Young men produce about 300,000 sperm per minute, about 400 million per day.
The new study was published on July 25, 2017, in the journal Human Reproduction Update titled Temporal trends in sperm count: a systematic review and meta-regression analysis. Levine et al (2017) used 185 studies (n=42,935) and showed a sperm count (SC) decline of .75 percent per year, coming out to a 28.5 percent decrease between 1975 and 2011. Similar declines were seen in total sperm count (TSC) while 156 estimates of serum volume showed little change.
Figure 2a shows the mean sperm concentration between the years 1973 and 2011. Figure 2b shows the mean total sperm count between those same years.
Figure 3a shows sperm concentration for the West (North America, Australia, Europe and New Zealand) vs Other (South America, Asia, and Africa), adjusted for potential confounders such as BMI, smoking etc. Figure 3b shows total sperm count by fertility and the West and Other. You can see that Fertile Other had a sharp increase, but the increase may be due to limited statistical power and a lack of studies of unselected men from those countries before 1985. There is a sharp increase for Other, however and so the data does not support as sharp of a decline as observed in Western countries.
If this is true, why is this happening? Factors that decrease spermatogenesis include (but are not limited to): obesity, smoking, exposure to traffic exhaust fumes, and combustion products. Though there is no data (except animal models) that lend credence to the idea that pesticides, food additives, etc decrease spermatogenesis (Sharpe, 2010). Other factors are known to cause lower SC which includes maternal smoking, alcohol, stress, endocrine disruptors, persistent and nonpersistent chemicals, and, perhaps most importantly today, the use of mobile phones and the wireless Internet (Virtanen, Jorgansen, and Toparri, 2017). Radiation exposure due to constant mobile phone use may cause DNA fragmentation and decreased sperm mobility (Gorpinchenko et al, 2014). Clearly, most of this decrease can largely be ameliorated. Exercise, eating right, and not smoking seem to be the most immediate changes that can and will contribute to an increase in SC in Western men. This will also increase testosterone levels. The cause is largely immobility due to the comfortable lifestyles that we in the West have. So by becoming more active and putting down smartphones, we can then begin to reverse this downward trend.
Saladin (2010: 1067) also states that pollution has deleterious effects on reproduction—and by proxy, sperm production. He states that the evidence is mounting that we are showing declining fertility due to “anatomical abnormalities” in water, meat, vegetables, breast milk and the uterus. He brings up that sperm production decreased in 15,000 men in 1990, decreasing from 113 million/ml in 1940 to 66 million/ml in 1990. Sperm production decreased more, he says, since “the average volume of semen per ejaculate has dropped 19% over this period” (Saladin, 2010: 1067).
Saladin (2010: 1067) further writes:
The pollutants implicated in this trend include a wide array of common herbicides, inseciticides, industrial chemicals, and breakdown products of materials ranging from plastics to dishwashing detergents. Some authorities think these chemicals act by mimicking estrogens by blocking the action of testosterone by binding to its receptors. Other scientists, however, question the data and feel the issue may be overstated. While the debate continues, the U.S. Environmental Protection Agency is screening thousands of industrial chemicals for endocrine effects.
Is it really true?
As seen above, the EPA is investigating whether thousands of industrial chemicals of effects on our endocrine system. If this is true, it occurs due to the binding of these chemicals to androgen receptors, blocking the production of testosterone and thusly sperm production. However, some commentators have contested the results of studies that purport to show a decrease in SC in men over the decades.
Sherins and Delbes are critical of such studies. They rightly state that most of these studies have numerous confounds such as:
1) lack of standardized counting measures, 2) bias introduced by using different counting methodologies, 3) inadequate within-individual semen sampling in the analysis, 4) failure to account for variable abstinence intervals and ejaculatory frequency, 5) failure to assess total sperm output rather than concentration, 6) failure to assess semen parameteres other than the number of sperm, 7) failure to account for age of subject, 8) subject selection bias among comparitive studies, 9) inappropriate statistical analysis, 10) ignoring major geographic differences in sperm counts, and 11) the causal equating of male ferility with sperm count per se.
Levine et al (2017) write:
We controlled for a pre-determined set of potential confounders: fertility group, geographic group, age, abstinence time, whether semen collection and counting methods were reported, number of samples per man and indicators for exclusion criteria (Supplementary Table S1).
So they covered points 1, 2, 4, 5, 6, 7, 8, 9, and 10. This study is very robust. Levine et al (2017) replicate numerous other studies showing that sperm count has decreased in Western men (Centola et al, 2015; Senputa et al, 2017; Virtanen, Jorgensen, and Toparri, 2017). Men Southern Spain show normal levels (Fernandez et al, 2010), while Southern Spanish University students showed a decrease (Mendiola et al, 2013). The same SC decrease has been noted in Brazil in the last ten years (Borges Jr. et al, 2015).
However, te Velde and Bonde (2013) in their paper Misconceptions about falling sperm counts and fertility in Europe contest the results of studies that argue that SC has decreased within the last 50 years stating that, for instance in Denmark, the median values remained between 40-45 million sperm per ml in the 15 years analyzed. They also state that declining birth rates can be explained by cultural and social factors, such as contraception, the female emancipation, and the second demographic transition. Clearly, ferility rates are correlated with the human development index (HDI) meaning that more developed countries have a lower birth rate in comparison to less developed countries. I believe that part of the reason why we in the West have lower birth rates is because there are too many things to for us to do to occupy our time, time that could be used to have children, like going to school to pursue Masters degrees and PhDs, to just wanting more ‘me time’.
Te Velde and Bonde (2013) conclude:
‘Whether the sperm concentration and human fecundity have declined during the past 50 years is a question we will probably never be able to answer’. This statement by Olsen and Rachootin in 200348 still holds for sperm concentration despite the report in 1992. In the meantime, we know that the results of oft-repeated studies from Copenhagen and Malmö do not indicate any notable change in sperm count during the last 10–15 years. Moreover, none of the available evidence points to a decline in couple fecundity during the last 30–40 years, including Denmark.28 Moreover, birth rates and TFRs instead of declining are on the increase in many EU countries, including the spectacular rise in Denmark.34
Echoing the same sentiments, Cocuzza and Esteves (2014) conclude “that there is no enough evidence to confirm a worldwide decline in sperm counts or other semen parameters. Also, there is no scientific truth of a causative role for endocrine disruptors in the temporal decline of sperm production as observed in some studies. We conjecture that a definite conclusion would only be achieved if good quality collaborative long-term research was carried out, including aspects such as semen quality, reproductive hormones, and xenobiotics, as well as a strict definition of fecundity.” Merzenich, Zeeb, and Blettner (2010) also caution that “The observed time trend in semen quality might be an artefact, since the methodological differences between studies might be time dependent as well. Intensive research will be necessary in both clinical and epidemiological domains. More studies are needed with strict methodological standards that investigate semen quality obtained from large samples of healthy men representative for the normal male population.”
Clearly, this debate is long and ongoing, and I doubt that even Levine et al (2017) will be good enough for some researchers.
There are various papers for and against a decrease in sperm production in the West, just like with testosterone. However, there are ways we can deduce that SC has fallen in the West, since we have definitive data that testosterone levels have decreased. This, then, would lead to a decrease in sperm production and then fecundity and number of children conceived by couples. Of course, sociocultural factors are involved, as well as immediate environmental ones that are immediately changeable. Even if there is no scientific consensus on industrial chemicals and effects on the endocrine system, you should stay away from those too. One major reason for the decrease in sperm production—if the decrease is true—is increased mobile phone usage. Mobile phone usage has increased and so this would lower SC over time.
Whether or not the decrease in SC is true or not, every man should take steps to lead a healthier lifestyle without their cell phone. Because if this decrease is true (and Other doesn’t show a decrease as well) then it would be due to the effects of our First World societies, which would mean that we need to change how we live our lives to get back on the right track. Clearly, we must change our diets and our lifestyles. I’ve written numerous articles about how testosterone is strongly mediated by the environment, and that testosterone production in men has decreased since Western men have been, in a way, feminized and not been as dominant. This can and does decrease testosterone production which would, in turn, decrease sperm production and decrease fertility rates.
Nevertheless, taking steps to leading a healthier lifestyle will ameliorate a ton of the problems that we have in the West, which are mainly due to low birth rates, and by ameliorating these problems, the quality of life will the increase in the West. I am skeptical of the decrease due to what was brought up above, but nevertheless I assume that it is true and I hope my readers do too—if only to get some fire under you to lead a healthier lifestyle if you do not do so already as to prevent these problems before they occur and lead to serious deleterious health consequences.
(I am undecided leaning towards yes. There are too many behaviors linked to lower SC which Western men partake in. There are numerous confounds which may have not been controlled for, however knowing the main reasons why men have lower sperm count and the increased prevalence in these behaviors, we can logically deduce that sperm count has fallen too. Look to the testosterone decrease, that causes both low sperm count and lower fertility.)