Male sperm quality plummets, is humanity facing a population crisis?

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Hello everyone, I'm Tiangeng. In October 2022, a study from Israel became a hot topic at home and abroad, sparking heated discussions. A research team led by Professor Hagai Levin of the Hebrew University of Israel conducted a meta-analysis of 223 studies on 57,000 male samples collected from 53 countries in the 20th and 21st centuries around the world and found that in less than 50 years, the average sperm count and sperm concentration of men worldwide have dropped by more than 50%, which can be described as a cliff-like drop. The article was titled "Contemporary Trends in Sperm Counts, a Systematic Review and Regression Analysis of Global Sperm Samples in the 20th and 21st Centuries" and was published in the journal "Progress in Human Reproduction".

The article caused an uproar in public opinion, with people discussing whether the results of the study represent a decline in male fertility, whether it indicates that the population will increase more slowly in the future, what causes this phenomenon, and what humans can do to deal with this worrying decline. Today we will introduce Professor Levine's interpretation of the findings of this study in detail.

The professor's research found that the decline in male sperm count and sperm concentration is global, and has occurred in various countries such as Asia, North America, Europe, Africa, and South America. The decline in sperm count has also gradually accelerated in the 21st century, showing an accelerating downward trend. Does this mean that population growth will become slower? The world population just reached 8 billion not long ago, and the world has added 1 billion people in 12 years. Does this research result indicate that the next 9 billion will come later? The answer is not completely certain. Although sperm count and concentration will affect male fertility, since population growth depends on many other factors, including social, economic, educational, behavioral, etc., even if sperm count drops by 50%, the impact on the number of children born to each woman is small. Therefore, it is impossible to show with certainty what kind of restrictions this phenomenon will impose on population growth.

We cannot predict the future, but we need to be prepared for various possibilities. What is more noteworthy is that the number and concentration of sperm not only reflects the ability to conceive, but also represents an indicator of the overall health of men and humans. Low sperm counts may lead to increased disease risks and increased male mortality, which means that it not only affects fertility issues, but also affects men's health. So what is the reason for this phenomenon? According to a series of studies on humans and animals by researchers, testicular development is an important factor affecting sperm count and sperm concentration. Testicular development is very sensitive to environmental factors. If we are exposed to chemicals that disrupt our hormones during fetal period, such as phthalates (a substance added during the plastic manufacturing process, which has a significant impact on fetal hormone function and normal testicular development) or common pesticides, it will disrupt our hormones during fetal period and even in adulthood. In addition, some unhealthy lifestyle habits, such as long-term consumption of ultra-processed foods, smoking, alcoholism, lack of physical exercise, staying up late, etc., will affect sperm concentration and sperm count.

In my country, the problem of sperm quality is equally serious. According to the latest data from the Zhejiang Human Sperm Bank, about 1,500 men sign up to donate sperm each year, but only about 400 pass the screening, with a pass rate of less than 27%. When it was just approved in 2005, the pass rate was 40%! This significant decline in quality also occurred in the Hunan Human Sperm Bank, where the sperm pass rate dropped from 55.78% in 2001 to 17.8% in 2015. These shocking data continue to attract people's attention, so what can humans do to deal with this worrying decline? This issue can be divided into two aspects: the public level and the personal level. At the public level, this significant and continuous decline in sperm quality will be a major public health issue. Dozens of experts and scholars in related fields, including Professor Galevin, also issued a joint statement at the 13th International Economics Seminar, calling on governments, the scientific and medical communities of various countries to recognize the importance of male reproductive health to human survival, and calling on researchers to conduct in-depth research on the causes of this continuous decline and curb this severe decline as soon as possible.

On a personal level, we are not helpless. Although it is unrealistic to completely avoid exposure to chemicals in today's society, protecting pregnant women and improving personal lifestyle habits can also be effective ways.

1. Maintain a regular work and rest schedule and avoid staying up late as the increase in prolactin will affect the production of male sperm.

2. Quit smoking and drink less alcohol. Tobacco and alcohol will affect sperm vitality and sperm integrity, affecting fertilization and embryo quality. In particular, cigarettes contain nicotine, carbon monoxide, chromium and other harmful substances, which not only affect the reproductive cells of male testicles, inhibit the secretion of sex hormones and kill sperm, but also easily interfere with the normal spermatogenesis process of the testicles, leading to a decline in semen quality and thus a decrease in sperm fertilization ability.

3. Avoid high temperature environment. Working in a high temperature environment for a long time, or frequently going to saunas and steam baths will affect the quality of sperm. The testicles and epididymis are located outside the body, not in the abdominal cavity, which means that mature sperm are more suitable for a relatively low temperature environment. Long-term high temperature will damage sperm, so sperm will also be affected when you have a fever.

4. Pay attention to hygiene and avoid genital infection. Infection or inflammation of the male genitals will affect the quality of sperm. Inflammatory cells will secrete inflammatory factors locally, causing damage to sperm.

5. Avoid radiation, toxic and harmful substances, and certain drugs such as ketoconazole, glucocorticoids, anti-tumor drugs, etc., which reduce sperm hormones by destroying the life tubules. Therefore, before taking the medicine, pay attention to whether the medicine has reproductive toxicity on the instructions.

Professor Hageranwen's research has sounded the alarm for all human society. This is a crisis situation that requires the attention of everyone and the cooperation of all sectors of society to be effectively resolved before it reaches an irreversible turning point.

This article is a work supported by Science Popularization China Starry Sky Project

Team/Author Name: Tiangeng

Review: Tao Ning

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.