The menacing decline in human sperm count

Nandkumar M. Kamat

This article addresses global and national concerns over falling male sperm counts. Finally, all discourses on demographics, birth rate, population growth or decline, genetic fitness of human progeny, rising issues of infertility, the booming business of assisted reproduction, and male obsession over erectile dysfunction converge to only one important cell – the human sperms.

Human semen with healthy sperm counts and healthy sperm is the key to the future of our species. However, under complex scenarios of climate change, air and water pollution, lifestyle, and dietary and nutritional changes, does human sperm have any future, or, as predicted by experts, does humanity face a sterile future?

Nobody is talking about the rapid decline in male sperm counts. Over the last five decades, significant declines in male sperm counts have been reported worldwide, raising concerns about male infertility, chromosomal damage, and their implications for human reproduction. The emergence of micro-plastic detection in human semen has added a new dimension to the crisis, particularly in densely populated countries like India. These findings emphasise the urgent need to address environmental and lifestyle factors contributing to declining male fertility.

A meta-analysis by Levine et al. (2017) revealed a 59.3% decline in total sperm count and a 52.4% decline in sperm concentration among men in North America, Europe, Australia, and New Zealand between 1973 and 2011. The study analysed 185 studies with over 42,000 men, indicating an annual decline of 1.4% in sperm counts. An updated analysis by Levine et al. (2022) found that sperm counts are decreasing at an even faster pace globally, highlighting a potential reproductive crisis.

India mirrors global trends with significant declines in sperm quality. Agarwal et al. (2015) reported that the average sperm concentration among Indian men dropped from 113 million/mL in the 1980s to 49 million/mL in the 2010s. Environmental pollution, pesticide use, stress, and urbanisation exacerbate the issue in India, where cultural and demographic dynamics depend heavily on fertility.

The declining sperm count directly contributes to male infertility, with around 15% of couples worldwide experiencing infertility and male factors accounting for 20-30% of cases (WHO, 2020). Poor sperm quality, reduced motility, and abnormal morphology are key factors. Lower sperm counts and poor quality increase the risk of DNA fragmentation and chromosomal abnormalities, which can lead to miscarriages, congenital disabilities, and developmental disorders in offspring (Aitken et al., 2014).

Fertility rates are falling globally, with India’s fertility rate dropping from 5.9 children per woman in 1951 to 2.0 in 2023 (United Nations, 2023). Declining sperm counts contribute significantly to this trend alongside socio-cultural factors like delayed marriages and contraception use.

Recent research has uncovered micro-plastics in human semen, suggesting a new environmental threat to male fertility. Studies have identified micro-plastic particles in human tissues, including blood and reproductive fluids (Ragusa et al., 2021). Micro-plastics, often containing endocrine-disrupting chemicals (EDCs), pose multiple risks. They can disrupt sperm production and function by inducing oxidative stress and inflammation, reducing sperm motility, and impairing DNA integrity. They are also carriers of EDCs such as bisphenol A (BPA) and phthalates, which interfere with testosterone production and other hormonal pathways essential for spermatogenesis (Swan et al., 2021). Micro-plastics can cross the placental barrier, raising concerns about their impact on foetal development and inter-generational reproductive health. Prolonged exposure to micro-plastics has been associated with reduced sperm counts and abnormal morphology in animal studies, raising alarms about potential human impacts (Zhang et al., 2022).

Beyond micro-plastics, other pollutants like pesticides, heavy metals, and industrial chemicals exacerbate sperm count declines. Studies in India have linked agricultural pesticide exposure to reduced sperm quality (Mathur et al., 2020). Obesity, smoking, alcohol consumption, and sedentary behaviour contribute to lower sperm counts. Sermondade et al. (2013) found that obese men exhibited 20% lower sperm concentrations compared to those with healthy body weights. Prolonged exposure to heat from occupational hazards or lifestyle choices, such as laptops on laps, impairs sperm production. Chronic stress affects the hypothalamic-pituitary-gonadal axis, reducing testosterone levels and impairing sperm production (Chen et al., 2016). Micronutrient deficiencies, particularly zinc, selenium, and antioxidants, are linked to poor sperm quality. Diets rich in processed foods and low in fresh produce exacerbate this issue. With age, sperm quality deteriorates. Studies show a significant reduction in motility and DNA integrity in men over 40 (Dain et al., 2011).

Levine et al. (2022) project that if the decline in sperm counts continues at the current pace, median sperm counts could approach zero by 2050. This raises the alarming possibility of widespread male sterility within this century. India faces unique challenges. While fertility treatments and assisted reproductive technologies (ART) can offer temporary solutions, they cannot fully offset the declining reproductive health of the population. Moreover, ART is inaccessible to all due to high costs and limited infrastructure.

The economic burden of infertility treatments is rising, with psychological and societal repercussions for affected couples. Declining fertility rates may lead to an aging population and shrinking workforce, posing significant challenges to economic sustainability.

The infiltration of micro-plastics and pollutants into human reproductive systems highlights the urgent need for environmental regulations to protect public health. Establishing longitudinal studies to monitor sperm quality trends and identify emerging threats like micro-plastics is essential. Enforcing strict controls on micro-plastic production and environmental pollution, particularly in urban and industrial areas, is vital. Public health campaigns should raise awareness about lifestyle choices that improve fertility, such as maintaining a healthy weight, avoiding smoking, and consuming a nutrient-rich diet. Expanding the availability and affordability of ART services, particularly in low-income and rural areas, is necessary. Encouraging the reduction of plastic use and promoting recycling initiatives can minimise environmental micro-plastic contamination.

Without urgent interventions, the possibility of widespread male sterility within this century is a real threat. Addressing this issue requires collaborative efforts between governments, researchers, and individuals to protect reproductive health and ensure the sustainability of human populations. While scientific advances in assisted reproductive technologies (ART) offer temporary solutions, they remain inaccessible to many due to economic, geographic, and social barriers. A multifaceted response is essential. Governments must enforce stricter regulations on industrial pollution, including micro-plastic production and waste management. Scientific research should focus on understanding how environmental toxins affect male fertility and develop preventive measures. Healthcare systems should prioritise fertility screenings and early interventions for at-risk populations. Public awareness campaigns should promote healthier lifestyles, including balanced diets, reduced tobacco and alcohol consumption, regular exercise, and stress management. Moreover, international cooperation is crucial. Integrating reproductive health into public health policies and educational curricula can ensure widespread understanding and proactive responses. The potential for widespread male sterility and its societal consequences are too significant to ignore.

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