Male Fertility Is Declining: What the Science of Sperm Reveals

Written by: Mate Health Clinical Education Team
Updated: July 2026

Large global meta-analyses report a substantial decline in average sperm concentration and total sperm count among men not selected by fertility status between 1973 and 2018. Newer U.S. research has not found the same clinically significant decline. The concern is credible, but its size, causes, and universality remain debated.

The Headline Number

The most widely cited estimate comes from Hagai Levine and colleagues. Their 2017 systematic review and meta-regression included 185 studies and 42,935 men who provided semen samples between 1973 and 2011.

Among men from North America, Europe, Australia, and New Zealand who were not selected based on fertility status, average sperm concentration declined by 52.4%, while total sperm count declined by 59.3%. [1]

A later global analysis added studies from South and Central America, Asia, and Africa and extended the collection period through 2018. It reported that the decline was not limited to Western regions and appeared to accelerate after 2000. [2]

Those findings concern sperm concentration and total sperm count. They do not prove that male fertility itself has fallen by the same percentage.

Fertility depends on multiple semen parameters, female-partner factors, age, timing, reproductive history, and other clinical conditions.

How Researchers Measured Sperm-Count Trends

Both Levine analyses used meta-regression, a method that combines results across many studies while accounting for study-level differences.

The researchers considered factors such as:

• Geographic region
• Whether participants were known to be fertile or were unselected by fertility status
• Age
• Abstinence period
• Semen collection methods
• Laboratory methods
• How sperm concentration and semen volume were measured

This approach can reveal patterns that smaller studies may miss, but it cannot eliminate differences in populations, laboratories, recruitment, or semen-analysis methods. The underlying studies were separate projects, not one continuous global monitoring program.

What the Global Update Added

The global update, published online in 2022 and in the 2023 journal issue, included data from 223 studies and more than 57,000 men across 53 countries. [2]

It added two important findings.

The Reported Trend Extended Beyond Western Countries

The analysis reported declining sperm concentration among unselected men from South and Central America, Asia, and Africa, regions that were underrepresented in the 2017 paper.

The Estimated Rate of Decline Increased After 2000

The authors reported a steeper annual decline in the post-2000 data. That finding raised concern that the trend was continuing rather than stabilizing.

The analysis identified a trend, not its environmental, medical, demographic, or lifestyle causes.

Is the Decline Real or a Measurement Artifact?

The global meta-analyses are influential, but they are not the only evidence.

A 2025 systematic review and meta-analysis examined 75 U.S. study populations representing 11,787 men without known infertility. It found no clinically significant decline in sperm concentration among confirmed fertile men or the broader U.S. population without known infertility. Total sperm count increased in the studies that provided enough information to calculate it. [3]

This does not disprove the global findings; the analyses used different populations, regions, periods, and models. It does show why "every man's sperm count is falling" is too broad.

The most accurate summary is:

• Large global meta-analyses report a substantial long-term decline, especially among men unselected by fertility status.
• Some newer analyses of fertile or U.S. populations report stable sperm concentration.
• Study heterogeneity, selection, laboratory methods, and geography remain important sources of uncertainty.
• The exact magnitude and clinical effect of any population decline remain debated.

This uncertainty is part of the science, not a reason to ignore the findings.

Testicular Dysgenesis Syndrome

One influential framework is testicular dysgenesis syndrome, or TDS.

First proposed by Niels Skakkebaek and colleagues in 2001, TDS links four male reproductive conditions:

• Impaired sperm production
• Testicular cancer
• Undescended testicles
• Hypospadias

The hypothesis proposes that these conditions may share origins in disrupted testicular development during fetal life. Environmental and hormonal influences during pregnancy are among the factors being studied. [4]

TDS is a research framework, not a clinical diagnosis given to an individual man. It also has not been proven to explain the reported global sperm-count trend by itself.

A later review argued that biological reproductive changes may be partly related to environmental exposures, including chemicals derived directly or indirectly from fossil fuels. That remains a scientific hypothesis requiring continued investigation. [5]

What May Be Driving the Trend?

No single cause has been established.

It is also important to distinguish factors associated with an individual man's semen quality from factors proven to explain a global population trend.

Endocrine-Disrupting Chemicals

Endocrine-disrupting chemicals can interfere with hormone signaling. Human evidence is strongest for certain phthalates and pesticides; findings for many other chemicals remain limited or inconsistent. [6]

Prenatal exposure may be especially relevant because testicular development begins before birth. However, observational human studies cannot easily prove that a particular chemical caused a later semen result.

Obesity and Metabolic Health

Obesity can alter reproductive hormones and metabolic health and is associated with semen changes, but it cannot explain every geographic or temporal trend.

Smoking, Alcohol, Diet, Sleep, and Stress

Smoking is consistently linked to poorer semen parameters. Heavy alcohol use, inadequate sleep, chronic stress, and lower-quality diets are also associated with semen differences, although findings vary.

These factors may contribute to individual risk. Their contribution to the reported global trend is harder to quantify.

Heat Exposure

Frequent or prolonged testicular heat may temporarily affect sperm production or semen quality. Everyday exposures vary greatly in duration and intensity, and no single heat source has been established as the primary cause of population-level sperm-count trends.

Microplastics

Microplastics are an emerging area of research, not an established explanation.

A 2024 study detected microplastics in semen samples from 40 men and reported associations between certain polymers and progressive motility. [7]

A separate multi-site study involving 113 men found that exposure to more types of microplastics was associated with lower total sperm count, concentration, and progressive motility. [8]

Both were observational and do not establish causation or prove that consumer changes improve fertility.

The likely explanation, if a broad decline is occurring, is not one "smoking gun." Multiple prenatal, environmental, medical, and lifestyle factors may interact.

Why Sperm Count Matters Beyond Fertility

Sperm count is only one part of fertility, but semen quality has also been studied as a possible marker of broader male health.

In a Danish cohort of 4,712 men, poorer semen quality was associated with greater long-term morbidity, particularly cardiovascular disease and diabetes-related hospitalization. [9]

A 2025 study following 78,284 men for up to 50 years also found an association between semen quality and lifespan. [10]

These studies do not show that low sperm count causes chronic disease or shorter life. Shared factors such as hormonal conditions, genetics, metabolic disease, inflammation, or environmental exposures may affect both reproductive and general health.

A semen analysis is not a general-health screening test. Still, substantially abnormal results may justify discussing broader health factors with a physician rather than viewing fertility as an isolated issue.

What Individual Men Can Control

Population findings cannot predict one man's results, and no lifestyle change guarantees fertility.

Reasonable steps include:

• Avoiding cigarettes and nicotine
• Limiting heavy alcohol use
• Maintaining a healthy weight and metabolic health
• Eating a balanced, minimally processed diet
• Exercising regularly without chronic overtraining
• Prioritizing adequate sleep
• Limiting frequent or prolonged high-heat exposure
• Reviewing testosterone, anabolic steroids, medications, and supplements with a physician

Reducing unnecessary exposure to plastics and other potential endocrine disruptors may be reasonable, but current research does not show that a specific product swap will reverse a low sperm count.

Men do not need routine serial semen testing simply because population averages may be changing. Testing is most useful when establishing a fertility baseline, evaluating delayed conception or known risk factors, or following a physician's recommendation.

Where the Research Goes Next

The central unanswered question is causation.

Researchers need:

• Prospective studies that measure exposures before changes in semen quality occur
• More standardized laboratory and recruitment methods
• Better geographic representation, particularly in regions with limited historical data
• Studies separating fertile, infertile, and unselected populations
• Research connecting semen trends to time to pregnancy and live birth
• Mechanistic studies explaining how specific exposures affect testicular and sperm function

Comparable repeated studies will be more informative than highly varied historical datasets.

What This Means for You

A population trend cannot tell you where you personally stand.

A semen analysis is the primary laboratory test for evaluating sperm production and semen quality. [12] Results are a clinical snapshot, not a diagnosis or fertility guarantee.

Mate Health's Comprehensive Semen Analysis reports 20 semen parameters, including volume, concentration, total sperm count, four motility classifications, morphology, velocity, and calculated functional sperm measurements.

The Advanced Semen Analysis adds DNA fragmentation, vitality, and sperm microscopy images.

Specimens are processed in a CLIA-certified, CAP-accredited high-complexity andrology laboratory using WHO 6th Edition (2021) methodology.

Patients receive a laboratory report along with access to MateIQ, which helps explain report values and questions they may want to discuss with their physician.

Abnormal findings or delayed conception may lead a physician to recommend repeat semen analysis, a physical examination, hormone testing, genetic testing, imaging, or other evaluation.

Curious where you personally stand? Explore Mate Health's at-home semen analysis options or learn more about our laboratory standards and specimen transport validation on the Mate Health science page.

FAQs

Are Sperm Counts Really Declining?
Large global meta-analyses report a substantial decline in sperm concentration and total count since the 1970s, including an apparent acceleration after 2000. A newer U.S. analysis found no clinically significant decline among fertile and unselected men.
The concern is credible, but the magnitude and universality of the trend remain debated. [1–3]

Does Declining Sperm Count Mean Male Fertility Has Fallen by 50%?
No. A decline in average sperm concentration is not the same as an equal decline in fertility.
Fertility depends on count, motility, morphology, DNA integrity, female-partner factors, timing, age, and other conditions.

What Is Causing Sperm Counts to Fall?
No single cause has been proven. Researchers are studying endocrine-disrupting chemicals, prenatal exposures, obesity, smoking, diet, sleep, stress, heat, and emerging contaminants such as microplastics.
Several factors may interact.

Will Sperm Counts Eventually Reach Zero?
Current studies do not support predicting that sperm counts will reach zero.
Population trends cannot be extended indefinitely in a straight line, and the average sperm concentrations reported in these meta-analyses remained above the WHO lower reference value. Continued monitoring is warranted, but "zero sperm by a certain year" is not an established scientific forecast. [1,2,11]

Can a Man Improve His Own Sperm Count?
Some semen parameters may change after addressing smoking, heavy alcohol use, obesity, heat exposure, medical conditions, or other modifiable factors.
Individual responses vary, and a different follow-up result does not prove that one change caused the difference.

Is Testicular Dysgenesis Syndrome a Diagnosis?
No. TDS is a research hypothesis linking impaired sperm production, testicular cancer, undescended testicles, and hypospadias through possible disturbances in fetal testicular development. [4]

Medical Disclaimer

This article summarizes epidemiological research for educational purposes and does not constitute medical advice or a personal diagnosis. Population trends do not predict individual fertility.

Consult a physician or reproductive urologist if you have fertility concerns, abnormal semen results, testicular symptoms, hormonal symptoms, or questions about medications that may affect sperm production.

Curious where you personally stand? Explore Mate Health's at-home semen analysis options or learn more about our laboratory standards and specimen transport validation on the Mate Health science page.

References

1. Levine H, Jørgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a systematic review and meta-regression analysis. Hum Reprod Update. 2017;23(6):646-659. doi:10.1093/humupd/dmx022. PMID: 28981654.
2. Levine H, Jørgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries. Hum Reprod Update. 2023;29(2):157-176. doi:10.1093/humupd/dmac035. PMID: 36377604.
3. Lewis K, Cannarella R, Liu F, et al. Sperm concentration remains stable among fertile American men: a systematic review and meta-analysis. Fertil Steril. 2025;123(1):77-87. doi:10.1016/j.fertnstert.2024.08.322. PMID: 39128669.
4. Skakkebaek NE, Rajpert-De Meyts E, Main KM. Testicular dysgenesis syndrome: an increasingly common developmental disorder with environmental aspects. Hum Reprod. 2001;16(5):972-978. doi:10.1093/humrep/16.5.972. PMID: 11331648.
5. Skakkebæk NE, Lindahl-Jacobsen R, Levine H, et al. Environmental factors in declining human fertility. Nat Rev Endocrinol. 2022;18(3):139-157. doi:10.1038/s41574-021-00598-8. PMID: 34912078.
6. Mínguez-Alarcón L, et al. Endocrine-disrupting chemicals and male reproductive health. Fertil Steril. 2023;120(6):1138-1149. doi:10.1016/j.fertnstert.2023.10.008. PMID: 37827483.
7. Li N, Yang H, Dong Y, et al. Prevalence and implications of microplastic contaminants in general human seminal fluid: A Raman spectroscopic study. Sci Total Environ. 2024;937:173522. doi:10.1016/j.scitotenv.2024.173522. PMID: 38802004.
8. Zhang C, Zhang G, Sun K, et al. Association of mixed exposure to microplastics with sperm dysfunction: a multi-site study in China. eBioMedicine. 2024;108:105369. doi:10.1016/j.ebiom.2024.105369. PMID: 39342804.
9. Latif T, Jensen TK, Mehlsen J, et al. Semen quality as a predictor of subsequent morbidity: a Danish cohort study of 4,712 men with long-term follow-up. Am J Epidemiol. 2017;186(8):910-917. doi:10.1093/aje/kwx067. PMID: 28498890.
10. Priskorn L, Lindahl-Jacobsen R, Jensen TK, et al. Semen quality and lifespan: a study of 78,284 men followed for up to 50 years. Hum Reprod. 2025;40(4):730-738. doi:10.1093/humrep/deaf023. PMID: 40037905.
11. World Health Organization. WHO Laboratory Manual for the Examination and Processing of Human Semen. 6th ed. Geneva: World Health Organization; 2021.
12. American Urological Association; American Society for Reproductive Medicine. Diagnosis and Treatment of Infertility in Men: AUA/ASRM Guideline, Part I. 2020; amended 2024.