Sperm Counts Are Falling. What’s Behind the Decline?

James Odell, OMD, ND, L.Ac.

Male reproductive health has experienced an unprecedented decline over the past five decades, characterized by substantial reductions in sperm count and testosterone levels.

This article will outline some of the current evidence on the global decline in sperm count and testosterone levels, examining underlying mechanisms, environmental factors, and clinical implications.

Oligospermia is the term used for low sperm count, or less than 15 million sperm per mL of ejaculate. The recognition of declining sperm counts began with the seminal work of Carlsen and colleagues in 1992, who reported a nearly 50% decrease in mean sperm concentration from 113 million/mL in 1940 to 66 million/mL in 1990 based on a systematic review of 61 studies. Their finding created intense scientific debate and subsequent investigations that have largely confirmed and extended these observations. More recently, comprehensive meta-analyses by Levine and colleagues have provided more evidence for a continuing and accelerating decline in sperm parameters, particularly among men from Western countries. Worldwide, multiple independent studies have documented an age-independent decline in testosterone levels, with population-level decreases of approximately 1% per year observed in American, Danish, Finnish, and Israeli populations.

In short, over the last 50 years, average human sperm concentrations dropped by 51.6 percent, and total sperm counts dropped by 62.3 percent, according to a 2023 study published in the journal Human Reproduction Update. This decline occurs independently of aging and is not fully explained by increases in obesity or other measured health factors, suggesting the involvement of environmental or lifestyle changes affecting entire populations. If this goes uncorrected the implications are more than concerning as infertility will be commonplace.

Causes of Oligospermia and Low Testosterone

The etiology appears to be multifactorial, involving endocrine-disrupting chemicals (bisphenol A, phthalates, pesticides, dioxins, microplastics, heavy metals), 5-G and other electrosmog factors, lifestyle factors (obesity, sedentary behavior, smoking, dietary toxins), deficient dietary nutrients (zinc, essential fatty acids), and insufficient sleep and chronic stress all contributing to a disruption of the hypothalamic–pituitary–gonadal (HPG) axis. At the cellular level, mechanisms include Sertoli and Leydig cell dysfunction, oxidative stress, mitochondrial impairment, and sperm DNA fragmentation. Integrated clinical management combining lifestyle optimization with dietary approaches, detoxification, mitochondrial support, antioxidant therapy, and targeted endocrine interventions is essential.

Obesity

Carrying excess weight significantly increases the odds of a low sperm count, and the risk climbs with each BMI category. Obesity has been shown to be one of the most significant modifiable risk factors for male reproductive dysfunction, with prevalence rates increasing dramatically worldwide over the past several decades. Obesity profoundly affects the HPG axis through multiple pathways. Increased adipose tissue enhances aromatase activity, converting testosterone to estradiol and creating a hyperestrogenic state that suppresses GnRH and gonadotropin secretion. Higher estrogen levels suppress the brain signals that drive sperm production. This leads to secondary hypogonadism, with reduced luteinizing hormone levels and decreased testicular testosterone production. Obesity also lowers testosterone directly, reduces levels of a protein that keeps sex hormones in balance, and increases scrotal temperature through fat deposits around the hips and groin.

Chronic low-grade inflammation associated with obesity directly impairs reproductive function. Adipose tissue in obese individuals secretes pro-inflammatory cytokines, including IL-6, TNF-α, and C-reactive protein (CRP), which suppress GnRH secretion, inhibit Leydig cell steroidogenesis, and induce oxidative stress in testicular tissue. Insulin resistance and hyperinsulinemia, hallmarks of metabolic syndrome, further impair Leydig cell function and spermatogenesis. Losing weight can reverse many of these hormonal shifts, though improvement in semen quality may lag behind weight loss by several months.

Interestingly, being underweight also raises the odds by about 46%, creating a J-shaped curve where extremes in either direction are harmful.

Smoking Tobacco and Excess Alcohol

Smoking tobacco has a clear, dose-dependent effect on sperm. Semen quality is roughly 22% worse in smokers compared to nonsmokers across multiple measures, including count, motility, and shape. Heavier smoking does more damage.

Alcohol’s impact depends entirely on how much you drink. Studies of over 8,000 healthy men found that moderate intake (around 8 units per week) did not significantly harm semen quality. But drinking more than 20 units per week was linked to longer time-to-pregnancy, and when both partners drank more than 4 units per week, live birth rates dropped by 21%. A unit is roughly one small glass of wine or half a pint of beer.

Endocrine-Disrupting Chemicals

The most common examples of endocrine disrupting chemicals (EDCs) include Bisphenol A (BPA), Phthalates, PFAS ("forever chemicals"), microplastics, parabens, dioxins, and certain agricultural pesticides like DDT, atrazine, and toxic metals. EDCs are synthetic or naturally occurring substances that mimic, block, or alter the body's natural hormones, impacting metabolism, growth, and reproduction. Phthalates are a group of chemicals found in plastics associated with food packaging, personal care products, and vinyl flooring. These are among the most studied environmental threats to sperm count. Numerous studies have shown strong evidence that higher exposure to the phthalate DEHP is associated with decreased sperm concentration. Among young Russian men, exposure to one specific phthalate during late puberty was linked to a 30 to 32% decline in sperm count by the time they reached sexual maturity.

Phthalate exposure has also been associated with increased odds of having no detectable sperm at all, with one study calculating 44% higher odds of azoospermia among exposed men. The chemicals appear to interfere with thyroid hormones and reproductive signaling hormones, which in turn impair semen quality. Pesticides and other endocrine-disrupting chemicals like BPA have shown similar associations, though phthalates have the strongest body of evidence.

Other endocrine disruptors include: 

• Butyl hydroxytoluene (BHT) is a preservative used in processed foods (anything with a shelf life that’s whole grain).

• tert-Butylhydroquinone (tBHQ) is used in processed foods. tBHQ can actually prompt an allergic response to wheat, milk, eggs, nuts, shellfish, and other foods; the additive may be partly to blame for the rise in food allergies. 

• Bisphenol A (BPA) is used in plaster water bottles, plastic lining in canned goods, and even baby teething rings.

• Methylparaben is used in multi-use drug containers (e.g. a bottle of novocaine). Methylparaben can cause an allergic reaction that is often mistaken for an allergy to the drug. 

• Parabens are used in sunscreen and cosmetics.

• Triclosan is used in hand sanitizers, soaps, deodorants, toothpaste, and other personal care products. Triclosan alters your holobiome, killing off many important microbes, promoting obesity, and even stimulating the growth of precancerous cells.

Reducing exposure is difficult since these chemicals are so widespread, but practical steps include avoiding microwaving food in plastic containers, choosing fragrance-free personal care products, and eating less processed and packaged food.

Toxic Metals

In addition to the many endocrine-disrupting chemicals associated with lower sperm count and quality are toxic metals. These include lead, cadmium, mercury, arsenic, and aluminum that are common environmental contaminants with well-documented reproductive toxicity. These metals bioaccumulate in tissues, including the testis, and exert toxicity through oxidative stress, disruption of cellular signaling, interference with essential metal homeostasis, and direct damage to cellular structures. A recent study examining the interaction of toxic metal exposure and oxidative balance score on semen quality found that metals like lead, mercury, and barium negatively correlate with semen quality parameters, with significant interactions between oxidative balance and metal toxicity. This highlights the importance of antioxidant status in modulating metal-induced reproductive toxicity.

Another potential source of aluminum exposure that deserves consideration is the use of aluminum-containing compounds as adjuvants in some vaccines. Aluminum salts have been used for decades to enhance the immune response to vaccination. Experimental studies of aluminum exposure, particularly in animals and at substantially higher exposures than those received through vaccination, have reported oxidative stress in testicular tissue, reductions in testosterone, and adverse effects on sperm count and quality. This raises the question of whether cumulative exposure to aluminum from all sources—including diet, drinking water, medications, occupational and environmental sources, and aluminum-containing vaccines—could contribute to reproductive toxicity in susceptible individuals. At present, however, human studies have not established that aluminum-containing vaccines reduce testosterone or sperm counts, and studies examining vaccination and male fertility have generally not demonstrated impaired semen parameters. Given the worldwide decline in male reproductive health and the widespread nature of aluminum exposure, further research examining cumulative aluminum burden, its various sources, and long-term reproductive outcomes would be valuable.

Mercury from contaminated fish and mercury amalgam fillings can cross the blood–testis barrier and impair spermatogenesis. Occupational exposure to mercury vapor in dental workers and industrial settings has been associated with reduced semen quality. Mercury induces oxidative stress, disrupts microtubule assembly in 4 developing spermatids, and can cause germ cell apoptosis. Arsenic, present in contaminated drinking water, can cause reproductive toxicity through oxidative stress, disruption of steroid hormone signaling, and epigenetic modifications. Studies in arsenic-endemic areas show associations between arsenic exposure and reduced semen quality, altered hormone levels, and increased infertility.

Cell Phones

In the last few decades, the universal use of mobile phones has contributed to radiofrequency electromagnetic radiation environmental pollution. The steady growth in mobile phone usage has raised concerns about the effects of phone radiation on male reproductive health. Most men store their cell phone in their pocket near their testicles. Exposure to non-ionizing radiation might induce damage to biological tissue organs, including the testis. It seems to be an apparent relationship between the increased exposure to mobile phone radiofrequency and sperm quality decline, but politics have gotten in the way of making finding public. Several studies show evidence of adverse effects of cell phone radiation on the male reproductive system, with a focus on sperm quality.  

Testicular infertility or testicular cancer due to mobile phone or microwave radiations suggests an increased level of reactive oxygen species (ROS). Though generation of ROS in testis has been responsible for possible toxic effects on physiology of reproduction, the reviews of last few decades have well established that these radiations are very harmful and cause mutagenic changes in reproductive pattern and leads to infertility.

Diagnostic Approaches

Evaluation of male reproductive dysfunction requires a comprehensive approach integrating clinical history, physical examination, hormonal assessment, and semen analysis. Given the multifactorial etiology of declining sperm count and testosterone levels, diagnostic evaluation should assess both reproductive parameters and potential contributing factors. Semen analysis remains the cornerstone of male fertility evaluation. Important parameters include semen volume, sperm concentration, total sperm count, progressive motility, total motility, and morphology. Unfortunately, conventional semen analysis has limitations, including high intra-individual variability, requiring at least two samples collected 2 to 4 weeks apart.

Hormonal evaluation should include measurement of total testosterone (preferably on a morning sample), luteinizing hormone (LH), follicle stimulating hormone (FSH), and estradiol. It is also informative to measure sex hormone-binding globulin (SHBG), a protein primarily produced in the liver that binds to sex hormones such as testosterone, dihydrotestosterone (DHT), and estradiol. By binding these hormones, SHBG regulates the proportion of hormones that are biologically active 5 versus those that are inactive in the bloodstream, ensuring proper hormonal balance and delivery to tissues and organs where they are needed. “Free” or bioavailable testosterone is more clinically relevant than total testosterone, particularly in older men or those with altered SHBG levels.

Environmental and occupational history is essential, given the role of endocrine-disrupting chemicals and other toxic exposures in male reproductive dysfunction. Many laboratories now can test for excess toxic elements (toxic metals) and pesticides. Some offer a comprehensive pesticide screening profile of over 400 commonly used agricultural pesticides.

Sperm Counts Are Falling: Can the Decline Be Reversed?

The fact that sperm counts have fallen across a short timescale of 50–70 years suggests that the causes must be lifestyle and environmental, rather than genetic. This also means that the decline is probably preventable, and possibly reversible. For this to happen, the problem must be recognized, its multi-causes made public and appropriate intervention or prevention implemented. 

Lifestyle factors, particularly the obesity epidemic, sedentary behavior, smoking, alcohol consumption, and chronic stress, contribute synergistically to reproductive dysfunction. The convergence of these factors in modern industrialized societies may explain the accelerating decline in sperm count observed post-2000. Emerging environmental threats, including air, water, food pollution, microplastics, and electromagnetic radiation add additional layers of complexity and concern to the reason why sperm counts are falling.

The reduced fertility of future generations is not the only impact the present decline in sperm counts will have on unborn children. There will also be the social impact of an ageing population, and an existential impact of whether future generations will come into being at all. This is not merely a medical issue but a societal imperative that demands the attention of policymakers, public health officials, clinicians, researchers, and the public.

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