Dr Michael Eisenberg is a professor of Urology at Stanford, a urologic surgeon, and a leading expert in male fertility and reproductive medicine.
It's no secret that global population decline is accelerating, but what's driving it? Male fertility might be a major piece of the puzzle. So why are so many men struggling with infertility and low testosterone, and what can be done to reverse it?
Expect to learn why global sperm counts have declined by over 50% in the last 40 years, what the biggest determining factors that influence a man’s sperm quality is, what men should do if they want to improve their sperm quality, what the relationship between age and fertility is for men and when fertility starts to drop off, if there is a relationship between sperm quality and there a relationship between alcohol, marijuana, smoking & vaping, what men can do to improve their testosterone, and much more…
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Chapters
0:00 - Why The Global Sperm Count Is Declining
7:11 - How Is Sperm Count Measured?
18:24 - The Impact Of Varicoceles On Fertility
27:01 - How Can Men Optimise The Quality Of Their Sperm?
33:47 - New Technology Changing Fertility Rates
38:26 - Is Testosterone Lowering Sperm Counts?
41:52 - Is Porn Affecting Erections?
55:30 - The Peak Fertility Checklist
01:01:16 - Find Out More About Michael
Global Sperm Counts Are Declining: What Men Need to Know About Fertility, Testosterone, and Modern Life
In recent years, scientists and clinicians alike have reached consensus on a troubling trend: global sperm counts have declined by more than 50% over the last 40 years. This isn’t just a statistical quirk—it’s a real, measurable phenomenon that signals broader health shifts for men and society. To unpack what’s driving this decline, why it matters, and what men can do, physician-researchers and urologists are digging deep into both the science and the lived experience of their patients.
The Data: Sperm Counts Are Down, Consensus Is Up
Early research on global sperm count decline began in the 1990s, and although initially controversial, multiple large-scale studies—including pivotal publications in 2017 and 2023—have solidified the reality: sperm counts have dropped by about 1% per year on average over the last half-century. More alarmingly, that rate seems to be accelerating to about 2% per year in the most recent decades.This isn’t just a regional or isolated phenomenon. While there are geographical differences—some reports even suggesting higher sperm quality in places like New York versus the Midwest—global trends are pointing unmistakably downward.
What’s Driving the Decline?
It’s Not Genetics. Evolution doesn’t act this quickly. Instead, attention has focused on environmental and lifestyle factors.Environmental Exposures: Microplastics, chemicals, and endocrine-disrupting compounds in our modern environment are under increasing scrutiny. Recent studies have detected microplastics in testicular tissue of both dogs and humans, with associations between higher microplastic load and poorer semen parameters.
Lifestyle Factors: Declining physical activity, rising obesity rates, poor diet, and increased exposure to environmental toxins all correlate with reduced semen quality. Emerging evidence also points to pesticide exposure, certain skincare and household product chemicals (like phthalates and phenols), and the widespread use of plastic packaging as possible contributors.
Health and Comorbidities: There’s a strong relationship between overall health and reproductive health. Men with hypertension, obesity, diabetes, or hyperlipidemia tend to have lower semen quality. More surprisingly, poor semen quality is associated not just with infertility, but also with higher rates of testicular cancer, prostate cancer, heart disease, diabetes, and even mortality. In large cohort studies, men with the lowest semen quality live three to five years less on average.
Sperm Count: The Main Marker—But Not the Only One
When clinicians assess male fertility, sperm count and concentration are primary metrics. While sperm shape (morphology) and motility (movement) matter, these parameters have been harder to track consistently over time due to changes in laboratory methods.Generally, men with at least 20–40 million motile sperm have a good chance of conceiving without assisted technology. Below this threshold, options include intrauterine insemination (IUI) and in vitro fertilization (IVF). It’s important to remember: sperm count isn’t a perfect predictor. Some men with very low counts conceive naturally, while others with high counts may struggle due to other factors.
Fertility and Health Are Linked
Fertility is a “team sport,” but the male contribution is often underestimated or evaluated late in the process. Half of all couples with fertility issues have a male factor, yet in the U.S., up to one-quarter of male partners are never seen by a reproductive specialist. Beyond sperm, a man’s reproductive health is closely tied to overall vitality—it’s no coincidence that “anything good for your heart is good for your fertility.”Common Correctable Issues: Varicocele, Hormones, and Lifestyle
- Varicocele: About one in seven men has a varicocele (dilated veins in the scrotum), which can impact sperm production and hormone levels. Surgical correction improves semen quality in about 70% of cases and may restore natural fertility in one-third to one-half.
- Hormonal Optimization: Low testosterone, as well as other hormone imbalances, may be amenable to medical therapy with agents like hCG and clomiphene, but testosterone replacement itself typically suppresses sperm production.
- Lifestyle: Quitting smoking, minimizing alcohol, maintaining a healthy weight, exercising regularly, getting sufficient (but not excessive) sleep, and reducing stress are simple but powerful interventions.
The Future: Assisted Reproduction, Genetics, and Need for Innovation
Assisted reproductive technologies like IVF and intracytoplasmic sperm injection (ICSI) are now responsible for roughly 2% of all births in the U.S.—a number that’s climbing. While these breakthroughs have helped many, they shift much of the treatment burden to female partners. There’s a pressing need for new treatments that can safely improve male fertility before high-tech interventions are required.IVG (in vitro gametogenesis) and embryo selection are on the horizon, with ethical debates intensifying over not just disease prevention but trait selection.
Testosterone: Also on the Decline
Just as troubling as declining sperm counts are falling rates of testosterone worldwide. Sedentary lifestyles, obesity, and environmental exposures again top the list of suspected causes. Testosterone and fertility are linked, but optimizing one doesn’t always improve the other—especially since exogenous testosterone suppresses sperm production.Erectile Dysfunction: A Barometer of Overall Health
Erectile function is most commonly tied to cardiovascular health and blood flow, not just hormones. The same risk factors—diabetes, hypertension, obesity, and smoking—apply. Erectile dysfunction can even predict heart disease years before other symptoms emerge.The rise of porn and changing sexual habits have brought new dimensions to psychogenic erectile dysfunction, especially in younger men, although most cases in older men remain vascular in origin.
Practical Checklist for Men’s Reproductive and Sexual Health
Non-Negotiables:- Exercise regularly.
- Maintain a healthy, balanced diet.
- Don’t smoke; limit alcohol and recreational drug use.
- Get 6–9 hours of quality sleep.
- Actively manage stress and mental health.
- Monitor and track baseline semen analysis and testosterone—even before trying to conceive.
- Use glass or stainless steel instead of plastic when possible.
- Choose organic produce where feasible and minimize exposure to pesticides and chemical-laden skincare products.
- Seek early evaluation by a reproductive urologist, especially if you notice any changes or are planning to start a family.
- Don’t wait for problems to arise—early knowledge enables better interventions.
Conclusion: Awareness, Early Action, and a New Era of Openness
Discussions about sperm count, reproductive health, and sexual function are losing their stigma as more men—and their partners—recognize their importance for long-term health and family-building. Platforms that encourage men to get checked early, educate about environmental risks, and advocate for healthier habits are a crucial part of reversing these worrying trends.Routine semen analysis and testosterone tracking may one day become as standard as cholesterol checks. For now, awareness and proactive engagement remain the best tools for men to safeguard not just fertility, but their lifelong health.
If you have questions about your reproductive health, consult a qualified medical provider or reproductive urologist. Early checks and lifestyle improvements are powerful tools in maintaining vitality for decades to come.
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