Dr. Shanna Swan has spent over 20 years studying the decline in sperm counts across America.
As a physician specializing in environmental medicine at Mount Sinai Medical Center in New York City, she has produced some of the most important research on this issue. She’s written books and frequently discusses the related decline in fertility.
So, when she noticed that her research was referenced by Health and Human Services Secretary Robert F. Kennedy Jr. shortly after his comments on October 16, she felt a wave of excitement.
At a press briefing, RFK Jr. stated: ‘Today, the average teenager in this country has 50 percent of the sperm count, 50 percent of the testosterone, as a 65-year-old man.’
It’s somewhat unclear whether RFK Jr. was comparing teenagers today with 65-year-olds today, or those 65-year-olds’ statistics from their teen years.
After his remarks, an HHS representative informed the Daily Mail that RFK Jr.’s claims stemmed from Dr. Swan’s 2017 paper.
Dr. Swan expressed her satisfaction to the Daily Mail, saying, ‘I am glad that sperm decline is getting some attention… and, well, I do have worries about fertility.’ She added, ‘I’ve been researching this since the late ’90s, so it’s heartening to see anyone, especially those in power, acknowledging it as an issue.’
Dr. Swan co-authored a 2017 study that sounded the alarm about a potential ‘spermageddon’ which could disrupt men’s fertility. By analyzing data from 1973 to 2011, the research revealed a 52 percent average decline in sperm counts, reducing the number available for fertilization.
This decline is considered a major factor in the increasing rates of male infertility, driven by sedentary lifestyles, rising obesity rates, and exposure to harmful chemicals.
Simultaneously, the U.S. total fertility rate has also dropped, from 2.52 births per woman in 1970 to 1.62 in 2023. Experts attribute this decline to various reasons, including a stronger focus on careers and financial concerns.
Although some studies suggest that sperm counts aren’t plummeting as drastically as initially reported, they nonetheless indicate a slight decline.
The HHS spokesperson also mentioned a different follow-up meta-analysis by Dr. Swan from 2022, which predicted average sperm counts could hit zero by 2045, potentially requiring couples to seek fertility treatment.
While Dr. Swan appreciated her research being referenced, she clarified that her work doesn’t support the claim that today’s teenage boys have sperm counts half of those of current 65-year-old men.
Instead, she suggests that what RFK Jr. likely meant was a comparison of current teenagers’ sperm counts—which are about 50 percent lower than those of today’s 65-year-olds when they were teenagers.
Sperm counts and testosterone levels are interlinked; increased testosterone fuels higher sperm production.
Dr. Swan stated, ‘Overall… sperm counts have decreased by about one percent annually since around 1973, and this rate has accelerated significantly in recent years. Testosterone levels are also dropping.’
In discussing the implications of decreasing sperm counts, she referenced a Danish study that highlighted how chances of conception diminish dramatically when sperm count falls below 40 million per milliliter, ultimately dropping to zero at zero sperm. Yet when the count reaches around 75 million, chances stabilize and remain effective, irrespective of whether it’s 75 or 150 million.
As we approach concerning levels, it’s becoming evident that getting pregnant is indeed taking longer—still possible, but more of a challenge.
Back in 2021, Dr. Swan warned that sperm counts could drop so low by 2045 that most couples may rely on assisted reproductive methods.
Nevertheless, some researchers have critiqued Dr. Swan’s findings, arguing that accurately counting sperm can be tricky for doctors.
The consensus is that factors reducing both sperm counts and testosterone levels are largely similar, with both affected by lifestyles, environmental hazards, and diet.
A study from this year by Cleveland Clinic researchers indicated that global sperm counts fell by an annual average of about 0.35 million sperm per milliliter between 1970 and 2018, describing it as a ‘modest annual decline.’ However, unadjusted figures from the same study suggested sperm counts in the U.S. held steady during that period.
The researchers doubted that even a modest decline would significantly impact infertility rates, estimating the average sperm count in the U.S. to be around 78 million per milliliter, which is comfortably within the range considered healthy.
Approximately nine percent of U.S. men are deemed infertile due to low sperm counts or insufficient sperm quality.
Globally, the number of men experiencing infertility has surged by 76 percent since the 1990s, while about 13.4 percent of women in the U.S. are infertile, with this rate remaining relatively unchanged recently.
Overall, one in six couples in the U.S. face difficulties conceiving.
Dr. Jeff Singer, a senior fellow at the Cato Institute, remarked that while RFK Jr. may have based his claims on genuine studies, his framing distorts the reality, conflating natural aging with an impending generational crisis.
Since the early 2000s, the fertility rate in America has been decreasing. The most recent data shows a rate of 54.5 births per 1,000 women aged 15 to 44 in 2023—down three percent from the previous year. The total number of births recorded in 2023 fell to 3.6 million, also down two percent from the prior year.
Experts are now warning of a potential ‘underpopulation crisis’ by 2050 if birth rates continue on this path, suggesting that the U.S. could risk extinction of its natural-born population in about 500 years.
