Scientists and physicians agree that there’s been a general decline in male fertility — but they aren’t sure why.

Social media buzz has pointed to a few environmental exposures as potential factors, including cellphones and electric vehicles.

But the reality is “more complicated” than that, according to experts who recently spoke to National Geographic.

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Although it’s not clear whether the decline is at a stage where it should be considered a crisis, numbers show that overall fertility — demographically measured by the number of babies born compared to women of child-bearing age — has decreased.

Dr. Alex Robles of the Columbia University Fertility Center in New York confirmed that clinical practitioners are “certainly seeing more couples where the male factor contributes to infertility.”

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“At least one-third of couples we evaluate have some male component,” he told Fox News Digital.

A 2017 meta-analysis published in Oxford Journals: Human Reproduction Update found that sperm counts in Western countries have declined by almost 60% globally since 1973. The 2023 update confirmed these same results.

Lead study author and epidemiologist Hagai Levine warned that this trend could lead to human extinction if it isn’t addressed.

“This is the canary in the coal mine,” Levine, public health physician at the Hebrew University-Hadassah Braun School of Public Health, told National Geographic. “It signifies that something is very wrong with our current environment, as lower sperm counts predict morbidity and mortality.”   

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These findings have been contradicted by other studies, however. A 2025 Cleveland Clinic analysis of studies from the last 53 years found sperm counts to be steady.

“There is no evidence to suggest that this decline is the cause of a precipitous decline in the ability to cause pregnancies,” primary study author Scott Lundy, a reproductive urologist at Cleveland Clinic, told National Geographic. “Most men, even with a modest decline in sperm counts, will still have no issues conceiving.”

Potential factors of decline

Multiple lifestyle factors can lead to a decline in male fertility, Robles noted, including obesity, smoking and diet, as well as environmental exposures and delayed parenthood.

National Geographic also reported that heavy drinking and marijuana use directly contribute to declining fertility and that quitting these habits, while also exercising and losing weight, can help.

Systemic inflammation, infection and disease can also have a “big, profound effect on the current status of fertility,” Lundy told National Geographic. 

Those who are getting over a fever from an infection, like the flu or COVID, will have a “drastically lower” sperm count for three months, he said.

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Male infertility can also be a marker of overall health, according to Robles. “Poor semen parameters are associated with other medical conditions and may signal underlying metabolic, hormonal or environmental issues,” he told Fox News Digital.

Allan Pacey, deputy dean of the Faculty of Biology, Medicine and Health at the University of Manchester, told National Geographic that the decline could be caused by increased use of contraception, as well as men waiting longer to have children or choosing not to have them at all.

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Microplastics have also been raised on social media as a potential culprit, but the effects are unclear, according to experts.

There is some evidence of endocrine-disrupting chemicals — which are substances found in reusable plastics and some disposable products — altering male fertility, Lundy revealed to National Geographic.

Myths busted

Concerns have circulated on social media that keeping a cellphone in a front pocket could harm male fertility. While Lundy said such an effect is biologically possible, there is currently no scientific evidence supporting the claim.

Another common myth is that infertility is mostly a women’s issue, Robles noted, but male factors contribute to about one-third to one-half of all cases.

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The claim that taking supplements can boost sperm counts is another common myth, he said, adding that it’s not backed by strong scientific evidence.

“Men should focus on factors that we know matter: maintaining a healthy weight, avoiding tobacco, limiting alcohol and managing chronic health conditions,” Robles advised. 

Experts recommend seeing a urologist to address fertility concerns. Robles said his approach begins with an evaluation, semen analysis, hormonal testing and medical history, while also exploring lifestyle factors.

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In addition to traditional treatment options, Robles said his fertility center also uses advanced tools that incorporate AI and robotics.

“Technologies like this are expanding options for patients who previously had very limited paths to biological parenthood,” he said.

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A new blood test could determine a woman’s dementia risk as early as 25 years before symptoms emerge.

That’s according to new research from the University of California San Diego, which found that a specific biomarker protein associated with early pathological processes of Alzheimer’s disease was “strongly linked” to future dementia risk.

The researchers analyzed blood samples from 2,766 participants in the Women’s Health Initiative Memory Study in the late 1990s, according to the study’s press release. 

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The women ranged from 65 to 79 years of age and showed no signs of cognitive decline at the start of the study.

After tracking the participants for up to 25 years, the researchers concluded that the biomarker phosphorylated tau 217 (p-tau217) was “strongly associated” with future mild cognitive impairment and dementia. 

Women who had higher levels of p-tau217 at the beginning of the study were “much more likely” to develop the disease. The findings were published today in JAMA Network Open.

“The key takeaway is that our study suggests it may be possible to detect risk of dementia two decades in advance using a simple blood test in older women,” first author Aladdin H. Shadyab, a UC San Diego associate professor of public health and medicine, told Fox News Digital. 

“These biomarkers may help us identify who is at greatest risk and develop strategies to delay or prevent dementia.”

“Our findings show that the blood biomarker p-tau217 could help identify individuals at higher risk for dementia long before symptoms begin,” he added.

This long lead time could open the door to earlier prevention strategies and more targeted monitoring, rather than waiting until memory problems are already affecting daily life, according to Shadyab.

“As the research advances, these biomarkers may help us identify who is at greatest risk and develop strategies to delay or prevent dementia,” he said.

This risk relationship wasn’t the same across the board, however. Women over 70 with higher p-tau217 levels had “poorer cognitive outcomes” compared to those under 70, as did those with the APOE ε4 gene, which is a known risk factor for Alzheimer’s disease.

The study also found that p-tau217 was a stronger predictor of dementia in women who were randomly assigned to receive estrogen and progestin hormone therapy compared to those who received a placebo.

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“Blood-based biomarkers like p-tau217 are especially promising because they are far less invasive and potentially more accessible than brain imaging or spinal fluid tests,” said senior author Linda K. McEvoy, senior investigator at Kaiser Permanente Washington Health Research Institute and professor emeritus at the Herbert Wertheim School of Public Health, in the release. 

“This is important for accelerating research into the factors that affect the risk of dementia and for evaluating strategies that may reduce risk.”

Blood tests for Alzheimer’s disease are still being studied and are not recommended for routine screening in people without symptoms, Shadyab noted. 

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More research is needed before this approach can be considered for clinical use prior to cognitive symptoms. 

Future studies should investigate how other factors — like genetics, hormone therapy and age-related medical conditions — might interact with plasma p-tau217, the researchers added.

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“The study examined only older women, so the findings may not necessarily apply to men or younger populations,” Shadyab noted. “We also examined overall dementia outcomes rather than specific subtypes such as Alzheimer’s disease.”