# Global human sperm count and fertility trends

The trajectory of human male reproductive health has become a focal point of intense epidemiological debate, clinical scrutiny, and public health concern. Over the past five decades, disparate datasets have yielded conflicting narratives regarding a global decline in sperm count and concentration. High-profile, retrospective meta-analyses have advanced a hypothesis of severe, accelerating reduction in global sperm metrics, linking these declines to widespread environmental degradation. However, a growing body of localized, prospective, and longitudinal research challenges the universality of this decline, offering alternative frameworks that prioritize biological variability and regional environmental factors. This report provides a comprehensive analysis of global sperm count data, the evolution of clinical reference standards, the methodological debates characterizing the research landscape, and the distinct environmental and metabolic mechanisms influencing human spermatogenesis.

## Evolution of Semen Quality Measurement and Clinical Thresholds

To evaluate longitudinal epidemiological data on semen quality, it is necessary to examine how the clinical definitions of baseline male fertility have evolved. For over forty years, the World Health Organization (WHO) has periodically published the *Laboratory Manual for the Examination and Processing of Human Semen*, establishing the standard reference intervals utilized by andrology laboratories and researchers worldwide [cite: 1, 2]. 

The reference ranges for critical semen parameters—sperm concentration, total motility, progressive motility, and normal morphology—have undergone significant revisions since the manual's first edition was published in 1980 to standardize global laboratory procedures [cite: 2]. The methodology for establishing these baselines shifted dramatically over time. Early editions relied largely on clinical consensus, whereas the fifth edition (published in 2010) and the sixth edition (published in 2021) established reference limits based on population data. Specifically, these recent guidelines set the lower reference limit at the 5th centile of populations of men whose partners achieved pregnancy within twelve months, theoretically grounding the metrics in proven biological fecundity [cite: 1, 2, 3].

This methodology resulted in the lowering of the threshold for "normal" sperm concentration. The fourth edition in 1999 established the minimum normal concentration at 20 million spermatozoa per milliliter [cite: 2]. The fifth edition lowered this to 15 million/mL, and the sixth edition slightly adjusted it to 16 million/mL [cite: 2, 3]. 

The clinical utility and epidemiological implications of these lowered thresholds remain heavily contested among andrologists. Several researchers argue that relying on the 5th centile of a fertile population fails to provide optimal prognostic value for fertility [cite: 1, 4]. Prospective studies of first-time pregnancy planners have demonstrated that male fecundity decreases progressively as sperm concentrations fall below 40 to 50 million spermatozoa per milliliter [cite: 4, 5]. 

The reduction of the clinical threshold to 15 million/mL created a vast clinical "grey zone" [cite: 4]. Men with concentrations between 15 million and 40 million/mL are classified as normozoospermic under recent WHO guidelines, yet statistical models indicate they possess a diminished probability of initiating a natural conception compared to men with concentrations above 40 million/mL [cite: 4, 5]. This shifting baseline complicates longitudinal meta-analyses, as historical cohorts measured against older, higher thresholds are frequently compared to modern cohorts measured against lowered standards, introducing diagnostic bias [cite: 1, 6].

### Standard Semen Parameter Definitions
Evaluating male reproductive potential requires examining multiple independent variables within an ejaculate, as isolated metrics do not fully capture fertilizing capacity [cite: 7, 8]:
* **Sperm Concentration:** The number of spermatozoa per milliliter of semen [cite: 7, 9].
* **Total Sperm Count (TSC):** The absolute number of spermatozoa in the entire ejaculate, calculated by multiplying the concentration by the total semen volume [cite: 7, 9].
* **Progressive Motility:** The percentage of spermatozoa capable of active, forward movement, a strict requirement for natural fertilization [cite: 7, 10].
* **Morphology:** The percentage of spermatozoa exhibiting a strictly defined standard shape and size. The assessment of normal forms is highly predictive of fertility, though reference values have dropped sharply to 4% under modern strict criteria [cite: 2, 3, 8].

| Parameter | WHO 1987 (2nd Ed.) | WHO 1992 (3rd Ed.) | WHO 1999 (4th Ed.) | WHO 2010 (5th Ed.) | WHO 2021 (6th Ed.) |
| :--- | :--- | :--- | :--- | :--- | :--- |
| **Sperm Concentration** | ≥ 20 million / mL | ≥ 20 million / mL | ≥ 20 million / mL | ≥ 15 million / mL | ≥ 16 million / mL |
| **Total Motility** | ≥ 50% | ≥ 50% | ≥ 50% | ≥ 40% | ≥ 42% |
| **Progressive Motility** | ≥ 25% | ≥ 25% | ≥ 25% | ≥ 32% | ≥ 30% |
| **Normal Morphology** | ≥ 50% | ≥ 30% | Not specified | ≥ 4% | ≥ 4% |

*Table 1: Evolution of WHO lower reference limits for human semen parameters (1987–2021) [cite: 2].*

## The Sperm Count Decline Hypothesis

The assertion that male fertility is undergoing a systemic, global collapse is primarily anchored by a series of expansive meta-regression analyses. This narrative gained initial prominence following a 1992 Danish study by Carlsen et al., which suggested a genuine decline in semen quality over the preceding 50 years [cite: 11, 12]. More recently, this paradigm has been formalized by Hagai Levine, Shanna Swan, and colleagues through major meta-analyses published in 2017 and 2022/2023.

In 2017, the Levine and Swan team published a highly influential meta-analysis encompassing 185 studies and representing over 42,000 men who provided semen samples between 1973 and 2011 [cite: 11, 13, 14]. This study reported a 52.4% decline in sperm concentration and a 59.3% decline in total sperm count [cite: 11, 13]. However, this data was limited almost exclusively to unselected men from North America, Europe, Australia, and New Zealand (categorized in the study as the NEA group) [cite: 11, 14, 15].

To address the lack of data from other regions, the research team published an updated systematic review and meta-regression analysis in *Human Reproduction Update* in late 2022 (and formally in 2023), incorporating an additional seven years of data collection (2011–2018) [cite: 15, 16, 17]. This updated analysis incorporated data from 53 countries, explicitly focusing on South and Central America, Asia, and Africa (the SAA grouping) [cite: 9, 16, 18]. The integration of this data formalized what is structurally known as the Sperm Count Decline (SCD) hypothesis on a global scale.

The numerical findings of the 2022 update indicate a steep downward trajectory. Among men unselected by fertility from all continents, the mean sperm concentration declined by 51.6% between 1973 and 2018, representing an adjusted slope of -1.17 million/mL per year [cite: 15]. Total sperm count experienced a commensurate 62.3% overall decline, dropping at a rate of -4.70 million per year [cite: 15]. On a population level, the global average sperm concentration was estimated to have dropped from 104 million/mL in 1973 to 49 million/mL by 2019 [cite: 5, 19].

Furthermore, the data analysis indicated a severe acceleration in this downward trajectory in recent decades. Prior to the year 2000, sperm concentration was modeled to be declining at a rate of 1.16% per year [cite: 15, 20]. Post-2000, the calculated rate of decline more than doubled to 2.64% per year [cite: 15, 20]. For unselected men, the slope for sperm concentration was significantly steeper when restricted strictly to post-2000 data (-1.73 million/mL/year) compared to the long-term historical trend [cite: 15].

The researchers leading these studies frame these findings as a critical public health crisis. They argue that declining sperm counts serve as a biomarker for broader male morbidity and mortality, linking the phenomenon to "testicular dysgenesis syndrome," increased risks of testicular cancer, genital birth defects, and systemic hormonal disruptions originating during fetal development [cite: 16, 18, 21]. Under the SCD framework, the global reduction in spermatogenesis is viewed as a "canary in the coal mine" reflecting systemic environmental degradation [cite: 9, 18, 22].

## Methodological Critiques and the Biovariability Framework

The overarching narrative of an uninterrupted, universal collapse in male spermatogenesis is heavily disputed within the fields of epidemiology and andrology. Critics argue that retrospective amalgamation of disparate historical studies requires vast statistical assumptions to normalize immense variations in geography, clinical population selection, laboratory methodology, and abstinence periods [cite: 19, 23, 24]. Specifically, laboratory methods for counting sperm have evolved significantly over the last 50 years; comparing historical hemocytometer counts with modern computer-assisted sperm analysis (CASA) introduces inherent baseline inconsistencies [cite: 23].

The most systemic critique of the SCD hypothesis originated from the Harvard GenderSci Lab, led by Marion Boulicault and Sarah S. Richardson [cite: 13, 25, 26]. In 2021, these researchers published a rebuttal framework termed the Sperm Count Biovariability (SCB) hypothesis [cite: 13, 22, 27]. The SCB hypothesis critiques the core assumptions of the SCD model on several scientific and demographic fronts:

### The Fallacy of the Historical Optimum
The SCD model implicitly assumes that the exceptionally high sperm concentrations recorded in Anglophone, developed nations during the 1970s represent the biological optimum or "species-typical baseline" for human males [cite: 22, 27]. The SCB framework argues there is no physiological or evolutionary basis to assume that averages near 100 million/mL are optimal simply because they were historically recorded [cite: 22, 27]. Because natural conception probabilities plateau rapidly above 40 to 50 million/mL, concentrations far exceeding this threshold do not confer additional reproductive advantages [cite: 4, 5, 22].

### Pathologizing Normal Variation
The SCB hypothesis asserts that sperm count naturally fluctuates within a wide, non-pathological range based on individual life-history traits, ecology, and geographic location [cite: 13, 22, 27]. A lower population average does not inherently signify a population-level disease state if the average remains safely above the threshold required for successful fertilization [cite: 22, 25]. The Harvard researchers argue that the SCD hypothesis incorrectly interprets benign or adaptive variation as a metric of toxicity and impending reproductive failure [cite: 22].

### Categorization Flaws and Socio-Political Co-opting
The researchers criticized the initial 2017 Levine meta-analysis for relying on blunt, geographically and racially fraught categorizations. Separating global data into "Western" (North America, Europe, Australia) and "Other" (South America, Asia, Africa) buckets obscures localized environmental data, ignores socioeconomic variables within those regions, and relies on colonial hierarchies of data valuation [cite: 12, 25, 26]. Furthermore, the researchers cautioned that the apocalyptic framing of the SCD narrative has been frequently co-opted by socio-political movements—specifically Alt-Right and white nationalist groups—to support unscientific claims regarding population replacement and the emasculation of men in "Western" nations [cite: 12, 26, 27].

| Feature | Sperm Count Decline (SCD) Hypothesis | Sperm Count Biovariability (SCB) Hypothesis |
| :--- | :--- | :--- |
| **Interpretation of Historical Data** | The 1970s data represents a healthy, species-typical baseline that modern populations have fallen from [cite: 22, 27]. | The 1970s data represents a single historical point; exceedingly high counts are not intrinsically optimal [cite: 22, 27]. |
| **Meaning of Sperm Count** | A direct proxy for systemic male health, morbidity, and environmental degradation [cite: 16, 22]. | A highly variable metric responsive to benign ecological and life-history factors; wide ranges are non-pathological [cite: 13, 22]. |
| **Clinical Implication of Decline** | Declining averages portend a looming global crisis of male subfertility and eventual population collapse [cite: 16, 22, 24]. | As long as variation remains above the critical fecundity threshold (40 million/mL), actual fertility is not severely impacted [cite: 4, 22]. |

*Table 2: Comparison of the core analytical frameworks characterizing modern sperm count research.*

## Regional Divergence in Longitudinal Studies

When isolated from broad, historical meta-analyses, recent longitudinal studies utilizing standardized methodologies within specific geographic regions frequently contradict the narrative of a synchronized global decline. An analysis of localized data reveals massive geographic heterogeneity, suggesting that sperm quality trends are highly dependent on regional environmental policies, local ecologies, and clinical population dynamics [cite: 28].

### North America and Europe
In the United States, a 2025 systematic review and meta-analysis conducted by researchers at the Cleveland Clinic evaluated 75 unique studies encompassing 11,787 American men without known infertility between 1970 and 2023 [cite: 29]. The researchers found no statistically significant decline in sperm concentrations across the 53-year period (P = 0.42) [cite: 29]. Conversely, among 49 of the studies that reported sufficient data to determine total mean sperm count, there was a statistically significant *increase* of 2.9 million spermatozoa per year between 1970 and 2018 (P = 0.03) [cite: 29]. 

Similar stability has been observed across broad areas of Europe. A 2023 meta-regression analysis by Cipriani et al. evaluated 62 articles encompassing over 24,000 men in the USA and Western European countries from 1993 to 2018 [cite: 6, 30]. The study found no significant downward trend in sperm concentration overall (p-value = 0.86) [cite: 30]. While minor negative trends were detected specifically in Scandinavian countries, the findings did not reach statistical significance, and no negative trends were observed in Central or Southern Europe [cite: 30]. 

Longitudinal stability has also been demonstrated in single-center analyses. A 16-year retrospective study (2008–2023) from a fertility clinic in Ireland involving over 15,000 men demonstrated a 22.8% *increase* in median sperm concentration, rising from 57 million/mL to 70 million/mL [cite: 31, 32]. The rates of clinical oligospermia (low sperm count) and azoospermia (absence of sperm) remained completely stable across the 16-year period [cite: 31, 32].

### Asia
In Asia, distinct regional studies reveal how rapidly changing environmental policies and diverse ecological conditions dictate semen quality. A 2026 retrospective cohort analysis of 5,886 healthy sperm donors at the Beijing Human Sperm Bank assessed trends from 2011 to 2018 [cite: 33]. The study recorded robust, statistically significant improvements across nearly all metrics: sperm concentration increased by 12.3% (reaching 96.5 million/mL in 2018), total sperm count increased by 18.7%, and the percentage of progressive motility improved significantly [cite: 33]. The researchers noted strong negative correlations between air pollutants (sulfur dioxide, nitrogen dioxide, PM10) and sperm quality. The documented improvements in semen parameters directly aligned with the implementation of China's aggressive 2013–2017 Air Pollution Prevention and Control Action Plan, demonstrating that environmental mitigation can rapidly reverse downward reproductive trends [cite: 33].

India presents a more polarized epidemiological picture. Clinical reports from urban centers frequently highlight sharp plummets in average sperm counts, with institutional observations suggesting a drop from 60 million/mL to 20 million/mL over the last three decades, exacerbated by urban pollution, heat stress, and metabolic syndrome [cite: 34, 35]. However, a rigorous 17-year scientific investigation (2006–2022) conducted by Kasturba Medical College in Southern India analyzed nearly 12,000 men and concluded that semen quality—including concentration, volume, and motility—had remained entirely stable for nearly two decades [cite: 36]. Other Indian studies highlight localized ecological impacts; for example, men living in high-altitude, hypoxic regions of Northeast India exhibit significantly worse semen parameters than those residing in plain regions [cite: 37].

### Africa
The data emerging from the African continent largely supports the narrative of localized reproductive distress, driven by unique environmental, socioeconomic, and infectious disease burdens. A 2023 systematic review of Sub-Saharan Africa identified massive temporal declines in sperm parameters between 2010 and 2019, including an 87% reduction in sperm concentration and a 55% reduction in normal morphology in countries such as Nigeria and South Africa [cite: 38]. 

Similarly, an analysis of men attending fertility clinics in urban Ghana found severe abnormalities [cite: 39]. The study documented an 80.5% prevalence of leukocytospermia (high concentrations of white blood cells in the semen, indicating severe reproductive tract inflammation or infection), and a staggering increase in clinical oligospermia from 20.5% to 57.6% over recent years [cite: 39]. In North Africa, a retrospective study encompassing over 21,000 men from Tunisia, Algeria, and Libya demonstrated a continuous decline in sperm morphology between 2013 and 2024, a deterioration that was temporarily exacerbated during the COVID-19 pandemic [cite: 40].

| Region | Study Period | Population Focus | Key Findings | Direction of Trend |
| :--- | :--- | :--- | :--- | :--- |
| **USA** (Lundy et al. 2025) [cite: 29] | 1970–2023 | 11,787 unselected/fertile men | No decline in concentration; 2.9 million/year increase in total sperm count. | Stable / Increasing |
| **Western Europe** (Cipriani et al. 2023) [cite: 30] | 1993–2018 | 24,196 men | No significant trend overall; Scandinavia showed slight non-significant decline. | Stable |
| **Ireland** (Nolan 2026) [cite: 32] | 2008–2023 | 15,413 fertility clinic patients | 22.8% increase in median sperm concentration; stable oligospermia rates. | Increasing |
| **Beijing, China** (2026 Study) [cite: 33] | 2011–2018 | 5,886 healthy sperm donors | 12.3% increase in concentration; 18.7% increase in total count. Linked to pollution reduction. | Increasing |
| **Southern India** (Andrology Center 2025) [cite: 36] | 2006–2022 | 12,000 fertility clinic patients | Stable semen quality across all parameters for 17 years. | Stable |
| **Sub-Saharan Africa** (2023 Review) [cite: 38] | 2010–2019 | Infertile men (Nigeria, S. Africa) | 87% decline in concentration; 55% decline in normal morphology. | Declining |

*Table 3: Summary of recent localized longitudinal studies demonstrating massive geographic heterogeneity in human semen quality trends.*

## Environmental and Lifestyle Determinants of Sperm Quality

Where localized declines in spermatogenesis do exist, they are increasingly linked to the "exposome"—the totality of environmental, occupational, and lifestyle exposures a human male encounters throughout life. Because spermatogenesis is a continuous, highly sensitive biological process characterized by rapid cell division, the male reproductive axis serves as an acute biological sensor for environmental degradation [cite: 10, 41].

### Microplastics and Endocrine Disruptors
Research conducted in 2024 and 2025 has provided definitive epidemiological evidence confirming the presence of microplastics and nanoplastics directly within human semen [cite: 42, 43]. A comprehensive multi-site study in China detected microplastics in 75% of human semen samples analyzed [cite: 43]. Using laser direct infrared (LD-IR) spectroscopy, researchers have identified multiple distinct polymer types, noting that the presence of specific plastics—notably polytetrafluoroethylene (PTFE) and polyethylene (PET)—is heavily correlated with profound cellular disruption [cite: 42, 44].

Microplastics inflict reproductive damage primarily through the generation of reactive oxygen species (ROS), highly unstable molecules that overwhelm the antioxidant defenses of the seminal plasma [cite: 43, 45]. This resulting oxidative stress damages the lipid-rich cell membranes of spermatozoa, severely limiting progressive motility, and compromises sperm DNA integrity [cite: 43, 45]. Animal models demonstrate that polystyrene microplastics can also act as endocrine-disrupting chemicals (EDCs) by binding to enzyme receptor sites in the gonads, triggering inflammation and disrupting the biosynthesis pathways of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone [cite: 45, 46]. In clinical observations, human participants exposed to multiple microplastic types exhibited significant, dose-dependent reductions in total sperm count and progressive motility [cite: 42].

### Ambient Temperature and Climate Change
Spermatogenesis is exquisitely temperature-sensitive. The physiological integrity of sperm production requires the scrotal environment to remain 2 to 4 °C below core body temperature (approximately 33–34 °C) to function efficiently [cite: 47, 48, 49]. When ambient heat exceeds this strict thermoregulatory threshold, the physiological cooling mechanisms of the scrotum (e.g., vascular heat exchange, muscular adjustment) are overwhelmed [cite: 47, 48]. 

Systematic reviews tracking the impact of global warming on fertility reveal a severe correlation between extreme heat exposure and diminished semen quality [cite: 47, 50]. Sustained elevations in testicular temperature disrupt the blood-testis barrier and induce apoptosis (programmed cell death) in developing germ cells, particularly during the highly sensitive meiotic and spermiogenic phases [cite: 47]. A massive retrospective study in Buenos Aires, evaluating over 54,000 men from 2005 to 2023, demonstrated that prolonged exposure to heat waves significantly reduced sperm concentration, total count, and normal morphology, with the damage heavily dependent on the duration of the heat event [cite: 50]. 

The impacts of thermal stress are magnified in specific geographical zones. Analyses utilizing NOAA temperature anomalies and World Bank fertility data from 1951 to 2023 demonstrated a stark negative correlation between rising temperatures and fertility rates [cite: 48]. South and East Asia have been identified as primary "hotspots" for heat-induced male reproductive decline; in these regions, high baseline temperatures compounded by the "Urban Heat Island" effect result in chronic thermal stress that continuously suppresses spermatogenesis [cite: 47, 51].

### Obesity and Metabolic Factors
The global rise in metabolic syndrome and obesity represents a dominant driver of diminished male fecundity. Extensive meta-analyses encompassing over 70,000 men confirm a direct, dose-dependent relationship between a high Body Mass Index (BMI) and poor semen quality [cite: 52, 53]. Men classified as obese experience consistent, statistically significant reductions in semen volume, total sperm count, and progressive motility [cite: 52, 54].

The pathophysiology of obesity-induced subfertility is multifactorial and heavily hormone-dependent. Excess adipose tissue acts as an active endocrine organ, over-expressing the aromatase enzyme, which facilitates the rapid conversion of circulating testosterone into estradiol (estrogen) [cite: 55]. This unnatural elevation of systemic estrogen suppresses the hypothalamic-pituitary-gonadal (HPG) axis, crashing endogenous testosterone production and starving the testes of the hormonal stimulation required to maintain spermatogenesis [cite: 55, 56]. 

Furthermore, obesity generates chronic, low-grade systemic inflammation and severe oxidative stress [cite: 54, 56]. This oxidative burden is clearly evidenced by the high DNA Fragmentation Index (DFI) consistently observed in the spermatozoa of obese men [cite: 56, 57]. High DFI directly correlates with reduced fertilization success, increased miscarriage rates, and poor embryonic development, making it a critical metric of subfertility that is entirely missed by traditional sperm counting methods [cite: 34, 55, 56].

## Reversibility and Public Health Implications

Despite the severity of environmental and metabolic stressors, a defining clinical reality regarding male fertility is its high degree of reversibility. Unlike the female reproductive system, which relies on a finite ovarian reserve established before birth, male spermatogenesis is a continuous, regenerative cycle [cite: 7]. The entire process of producing mature spermatozoa requires approximately 74 to 90 days [cite: 5, 58]. 

This brief regenerative window presents frequent opportunities for targeted clinical and public health interventions. Studies demonstrate that sperm quality parameters, including concentration and DNA integrity, show measurable improvements within months following weight loss, smoking cessation, or the removal of occupational hazards and toxicants [cite: 5, 41, 56]. Meta-analyses have confirmed that weight reduction in obese men ameliorates endocrine abnormalities, raises serum testosterone levels, and improves both qualitative and quantitative sperm parameters [cite: 56]. 

At the macro-level, population sperm counts serve as a highly responsive metric to environmental policy. The documented 12.3% improvement in sperm concentrations among Beijing donors between 2011 and 2018 stands as a powerful proof-of-concept; as aggressive national policies successfully mitigated atmospheric sulfur dioxide and particulate matter, the reproductive health of the local population recovered accordingly [cite: 33].

Ultimately, the global sperm count data does not unequivocally prove an irreversible, species-wide extinction event. Instead, it reveals a highly sensitive biological metric reacting acutely to modern industrial, chemical, and metabolic environments. While meta-analyses aggregating historical data show a significant downward shift over the late 20th century, contemporary longitudinal studies indicate that semen quality stabilizes or even improves when populations are protected from acute environmental degradation and metabolic disease. Acknowledging this biovariability, expanding diagnostic testing beyond basic counts to include DNA fragmentation, and focusing heavily on reversible lifestyle factors is essential for addressing modern male subfertility through targeted public health strategies [cite: 22, 34, 36].

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60. [time in Brazil](https://www.google.com/search?q=time+in+Brazil)
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72. [Trend of change of sperm count and concentration](https://pubmed.ncbi.nlm.nih.gov/36709405/)
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74. [Effects of SARS-CoV-2 infection on semen quality](https://tau.amegroups.org/article/view/136315/html)
75. [Trends in DALYs and prevalence of male infertility](https://pmc.ncbi.nlm.nih.gov/articles/PMC12631329/)
76. [Semen quality in hilly and plain regions of India](https://icr-heart.com/article/semen-quality-in-hilly-and-plain-regions-of-india-a-comparative-study-2441/)
77. [South and East Asia identified as hotspots of global warming related impacts on male fertility](https://technode.global/prnasia/south-and-east-asia-identified-as-hotspots-of-global-warming-related-impacts-on-male-fertility/)
78. [Ambient ozone exposure and semen quality](https://bmjopen.bmj.com/content/16/2/e109024)
79. [Male infertility in India: trends and causes](https://www.omnicuris.com/medshots/daily_updates/male-infertility-india-trends-causes)
80. [Lifestyle and hormonal factors affecting semen quality in Indian men](https://www.eurekalert.org/news-releases/1101467)
81. [Male infertility in Indian men linked to lifestyle choices](https://www.oncoscience.us/news/pr/male-infertility-in-indian-men-linked-to-lifestyle-choices-and-hormonal-imbalances/)
82. [No decline in semen quality in Southern India](https://www.andrologycenter.in/blog/no-decline-in-semen-quality-in-southern-india-what-a-new-17-year-study-really-shows/)
83. [Growing male infertility concern in India](https://health.economictimes.indiatimes.com/news/industry/only-1-in-4-indian-men-meet-normal-semen-parameters-experts-flag-growing-male-infertility-concern/129550178)
84. [time in India](https://www.google.com/search?q=time+in+India)
85. [time in China](https://www.google.com/search?q=time+in+China)
86. [Trends in semen parameters of infertile men in South Africa and Nigeria](https://www.researchgate.net/publication/370296271_Trends_in_semen_parameters_of_infertile_men_in_South_Africa_and_Nigeria)
87. [Trends in semen quality among North African men](https://pubmed.ncbi.nlm.nih.gov/41603461/)
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89. [Trends in Semen Quality: A Contrasting Perspective From a Single-Centre Review in Ireland](https://merrionfertility.ie/wp-content/uploads/2026/02/Andrology-2026-Nolan-Trends-in-Semen-Quality-A-Contrasting-Perspective-From-a-Single%E2%80%90Centre-Review-in-Ireland.pdf)
90. [Trends in Semen Quality: A Contrasting Perspective](https://pubmed.ncbi.nlm.nih.gov/41674371/)
91. [Reversibility of exposure to lifestyle and environmental factors](https://www.mdpi.com/1422-0067/26/6/2797)
92. [Sperm count documented to be in substantial and persistent decline](https://beyondpesticides.org/dailynewsblog/2022/11/sperm-count-documented-to-be-in-substantial-and-persistent-decline/)
93. [Decline in Sperm Count Environmental Ties](https://healthpolicy-watch.news/decline-in-sperm-count-environmental-ties/)
94. [The factors impacting male reproductive health](https://www.youtube.com/watch?v=fzXpCAbkyxM)
95. [Environmental exposures and human fertility](https://pmc.ncbi.nlm.nih.gov/articles/PMC11978412/)

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35. [indiatimes.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQEn27U_1fkaIxiGBlGMkjx_qQGGHxP7s15FM2oO48wjpDgnWL2SNzh_6Tysd4_9-x78D1EptWV8ddF-3j7KjNJmXzooEw8DVaJ0qGO-o6zgRCDT3pbTvn6amE1t99XKC9UAj6Uwm0MnegTY9XRvThlILNNMmrbSgijKLVJmFc8kcWk3MZb1xOloJy0l17t_72DTECyU8JIzVdtqet8jaI7L356KpnZnUbASncKyk8N8yQKhYaPUbM_CxoIB1iKiPsV-ZXmPOagyfIakyqJRJ5woA8dNYekYmd95_CZQ)
36. [andrologycenter.in](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQG9ThEkaf03geIzswZR5w8u7LjBc4s2uIsCc7BgpiPT-bdIY3apaWoqbJKu6mVY_jymdccd_4l8DoUq_l8_r1ifAUWoigbVfNF8Bu4QciEut9z6_3CmiQJLpy-Psdx8xEwj0H27-Lg1KwCSoNwFydVKDUyj2LsmxmElCpi5qhOYBz3wpOzbKQzJ3uvKk4fG4f5rc9Jgwr3kmCt_kubA853EskBUzA_vypmr7dS7KxE=)
37. [icr-heart.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHLX65gT-5RL-VasF0zo2nL5_AK0ZRba3anfxTHBGNWYEQJYSs6lGmG7exXmQe_aRNsAp0-Wla1jlBHXVUzlSdTMQrbPa-PilfHMD2265kslCnMyb1eRwNJ5TDvcg_AYcO8GqrOiv5NqLwub3jF5-yN95aIwyfY_o5DPbSuSMp74iJUr3uwGrrG6xGVrG2XKG1rWMko_uhsqFyT-16UASI=)
38. [researchgate.net](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHgD2qIof7SFdE1hp5zvJB_46h8x7ihXkqG_x1wZo5uwjStFnONXFPzGmhNloWmyjIda_OAWvZGDAazOddZ8SUX2XdgG6dwfNrejsc9PEm3jlCICyPxkpG2M4i37K05ocR8ImZpRrJpjBaAFdYnQHKmaZnZIYGRM1sucMcucCouZlUShrRuLzqEoqM9wNm0OWKh9UO74HV0insT9_JZpfFiEYX5nb3Tdc3LQY8EWIN8tw==)
39. [nih.gov](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHXIAEJNfh9v5x0iFJQRALwxjl1_SZgHY5r4IY2te1AGuK0N3-cG8bbe4HLYSbgrV34inWhOBkBkD0BFihrhbW8Ig01-6UGC5_z9rxE3WbhcowODN1NOC2lSBrqJrJaFxjCe87duWXvaA==)
40. [nih.gov](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGLf_ZtnJSm1bUzSijUaDO68J-hIf0_-jKr3MKA9A4sgrUPOpUThmSR4Rd8fkk2c-q8t8nJcfXNhNwAH-DrvwtimW7e7Py3cQTM7xA_HLrTYjtIYjxYzKftyBcHinHkiA==)
41. [mdpi.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQF01RfVUp9k9TG1e8Eu2OsKcYq1AV-35VBej6KM65fXN0ZHtNH5vzjp9mZ7ev1PMiAug9yFcs4In83BcKwdhSDfHYQ33_eaH-rdGP1GquKDzs_5uWK_441-3-ejyhRM)
42. [news-medical.net](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHj1DnHEaCffTlkZ-Hx9aqkBa6CIInbPraBraSJ0ZY9xy2vWsT6815zKG6P4b1KssREWnzirur3q7v5KZkzSoRzXky83YCRl_QtWMEr1HbY-yiFWOgP3cog6YA4bjcA1NrnNtovf9Cd5uV9t49T-3f49nK9GCEBWIzsZ-dCnkTTg-vBOTnerbZpsvBgItGaf8JbjQOp4Eg0cb4HKMo0kldKcvCzOxS7Ym0E1ijDXXuU2GjJJVASIhhnrLFd6QzZ)
43. [fertilovit.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHA16PtX1jHUOZIvCy49pD-wUxa6LNRiqEGLf27MiESq_vJ87CtAHXRQ93uD-7d93oGvkt_V14wvKMYCdXHQ17LQFm0DwOgbnX9YCGjbbvtZGwaNsv0ZbJiH6DYG9FcMcKhIddidOKs2ze-x-o49ByrDr-AswKUZOFTIHmovT4gxgVwQvzgBFehq4GbWFktttOAMOfLeV7UGS8sdJfbnJ0=)
44. [nih.gov](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFwTO8sC6WBkVmWMUYykx6_gjBCkQqB5R-SJtHez_2YAGgk1IzB4oecmG0ZnuDCwSIsDpE6N5QYJ2CCHZHcUL9CAAymyHHJEKaljecOooQi5U0o3TjD_F_Gcb98y_c9h8xv8Hz14SaXnQ==)
45. [mdpi.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFfKacMe2XPHjYhDQKV8toqPIGCwYEXf8ONNi_QJhcLNVr6fIsh98CwK0MMSGfM9JBaxR3IdZVVzoehHJiZXB5EleLVFxMbBThEaBIpvn8n7rUnlLJXeDFsPM6DRHw=)
46. [linfield.edu](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHHaNQ2A4Eehy3WxhYRa7pbahXUnyolLuR_ROzOr73r_uOxsqflHLXPkuw0QsCBTMJsydvI7Kpo9OfR3PeRlnManEKQR6-aKeXFypgd7mFGBcZw3J-3e98lHHNb43FNjjmf2ls5FgrzwOzhEovg3pgj-MJJKF7d9M3v3_7nt0vCiVu7GcGxXsy44SGzrqUbcw==)
47. [mdpi.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFq7xyqOo7mDEpFWDv11J39R-m_dq3yV-N7DDudqrfiSH8tc-dSHc14mZgZLY1pc668l2x3wth3y1tDj_7MaLIUCTlqhx59pQlesrnmnWS2XCghlviLamPJN3I_W5I=)
48. [preprints.org](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGq6T2ArQL0smfj405GltL_gHYcFyTL6a_VnRtpslaJAIpUyckpWb6ne4Y0NS_tpWskq9TOJsXKejqM1nVGK9U80faj31B9gpY99VWAjXIheogzSNtDClAA3-tsT8LTzYNHDe_dl5A=)
49. [nih.gov](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFovAkv_X1yW1U3GCslr9_wUWCzYhyTZZarg-BeLfP5mGtKmbL4lynw5cjmqVECROmmnNG0GKOZTM9Ty8MKh5XzRbnFTd8u6aV3F_OQWcpESW1arnUwERLlz_T_viFSRp2l5vorJY_VPg==)
50. [aakashfertilitycentre.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHIJT7dTFN-Gdbpdj3AlZcHr2nKsOOvliHZtCXZ2IV7YYqid5I9Jl-raCfEseU4uRLa0rEg0JRCQZHezcwTua0OwBYGdZ2fS9NQQW3OCM69sdxbbj6prrLjrI3kaPXeE2jymb5NOqg7BOxXYHsgZNG1PLp_DJJN1MVmyv5mL17HmcFz62pgQbkMCWspbczQ7wcagZn2Kwr0ABXMvyP06MI5YnYSKAv4krdMII00sslSnl1oR_z_ke3PUkatgsSt3chT)
51. [technode.global](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFYdGws0hf_ekWePPIVMONaEftLb5PlqitBSbWGL7kZhTqydEQbNArhTMSO-Z6IWILHQDXlBlfE_GRCYk3zM9oysyLuA_iNYxwRDNpH3kdaHtY_l0HtnmYYyvoqFakJPSlPGQL6n1WQW2PqJKDT6Fg272Ph4gldANbMAsXvcOvVW1dlOS2fBEkfVfR3XscT21msPH1zQcZC_-rXijNqp7OYYQeJ1QJIoVzlS7EcH_H2OKKO04MH)
52. [sciencealert.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQEyhYhCOVva7PB2_cZvlefTPDYwGprVD7fPd31Ast0f4Mij_755Hay7M_AZrbt9yLszbRkKkz03EjWiL7jREQjb8IftOB6umHADFueWmxTGNrGOsTuRA0D9X3wZ_MhlAemUdwzZ2GSSON5YcBjU_oGqoK4IBPdpyihG-U-j7A6mER9DgO-sIBzQe3cKlc3XhmZTMY92Pb_a9IbE)
53. [sochob.cl](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFj0jCBRxFCmf_gvxPWgh-1XcpYZpijm1gb4h4YhKsZfTxvaM3gvDoPRR9JjPtlekJEPmwL74bndlECUlRxbQgxmWrTggABjB3B9W0U_gkiTXqaS22SCGJYv8f60E_6yMWooW8MW5qewbaNgQXj_TvQOLdKcZ-Q-oYSDfnuNVIsaKN3yG_8ScfScqQAnuCrohvCv8MH3Iy7V27ajhX4NBs96G_2nSbviNVMmSnb0B4_z53U20KNmybkxhPPwsw=)
54. [oup.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFEfXtktuYhEvyKEVrUl2Lcy9pj-9JMoKaHjA7fB20lOxnXbrV5k6XeRIemrv1nV9BOJxNk0kPty0bts95AQr54GZFP-jBtsJ6e62bJ8wdw12w4gVAcx76bBv66bSgZf8t8-z08McfE_pc8Miuy6Q==)
55. [nih.gov](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGabt0uxN5DDfFvR-k9Jqbd77z_CR_vt_ihbHhaW3V9hD8iVfSvE8HX5_cWRF3ALn6egaBcfWqcqfMbWVBA11zI5YWWH6r2Z1yJGxHR3VHNXgiTKhxaV4u4P5RM9cuYpzqEg5xKUuRQNg==)
56. [mdpi.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHBTiFI0Q3QaGZU1ERvAWH3G01EmHw-q7fhSAgUeyTFL3pVSMOim_PH3B8_TlfMij-CfVGJxE9x-QU57zISYY73wNFsl5ZQmf9ul281mCWaiRdpdiIXzx4t4ukD8xUh)
57. [eurekalert.org](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFvBgfoLZMpkbfzSn02fEBH35vtPWz-GZo6H4pdHcH3skpeQd7I_HEhfaphxtjM8EK7VdeomjQCb_PsEXD4qlYIPbk_ovhbdQq4yqhfGDJAJu7NCzlhuF3XiEr_F1okQSdhhcCrkfo=)
58. [youtube.com](https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGwgjkngRa4Ox-9fuyti63O_8Lvd2T1LL3Ergkq5c34IKrY7vMY9Y4qIM9s2IszLPXGbsalOURSdf0OPhew2Qj82sEmoKEXPPxNZjQG_cgDmUKutZ_7-aECtTNp8Ovo2Zs_)