Penis length has grown 24% in recent decades.
KAREN WEINTRAUB | USA TODAY
Studies of men from around the world show that the length of the erect penis has grown 24% over the last 30 years. [что сов.пало]
That sounds like it would be good news but it concerns some male fertility experts.
"The million-dollar question is why this would occur," said Dr. Michael Eisenberg, a urologist and male fertility specialist at Stanford Medicine, who led the research, published Tuesday in The World's Journal of Men's Health.
Other research has shown that both sperm count and testosterone levels are falling.
Penile length may not be directly related to fertility, Eisenberg said, but anything that changes the reproductive system is fundamental to human existence and "something we should pay attention to and try to understand why."
What the study showed
Studies have measured penile length dating back at least 80 years, Eisenberg said.
He and his team compiled data from 75 studies conducted between 1942 and 2021, on nearly 56,000 men. They found the average erect penis length increased by 24% over the last 29 years.
The trend was apparent in different regions of the world, he said. "This was not isolated to a specific population."
The average length of the erect penis across all regions and decades was about 5.5 inches, the study found.
Dr. James Hotaling, a urologist and men's infertility specialist at the University of Utah Health, praised the study but said he's not yet convinced that penises are growing longer.
The simplest explanation, he said, is that the method of measurement has changed over the last 30 years – though there's no evidence that has happened.
Why study this?
Eisenberg got interested in the topic because of declining male sperm counts and testosterone levels. He thought research would show that penises are shrinking as these levels fall and men get more obese.
Instead, he found that they're growing and at a pretty fast clip. "It certainly was very surprising," he said.
Hotaling said it's unclear what the clinical impact of this finding might be, but he agreed that it contradicted his expectations. "This would not support the sperm apocalypse."
What might explain it?
Eisenberg thinks the change in length might be explained by earlier puberty. Boys, like girls, have been reaching puberty earlier in recent years. Perhaps, he said, that's giving their bodies a longer time to grow overall.
Hotaling wants more evidence. Sometimes early puberty stunts growth, he said, and it's not clear whether hitting puberty early makes puberty last longer.
It's probable, he said, that chemical exposures could affect penis length, but there's no evidence for that.
"If the findings were the opposite," and penises were shrinking, he said, "everybody would be freaking out."
Hotaling published a paper in 2021 showing that men with infertility have slightly shorter penises on average than men without infertility.
At the time, he thought the same biological factor – technically called testicular dysgenesis syndrome – might be behind both infertility and shorter length. But this study seems to go against that hypothesis.
"I don't have a great explanation for it," he said of the new finding. "I think it merits further investigation."
Hotaling said he hopes the research, whether supported in the future or not, will encourage men who are concerned to talk to their doctor.
"Anything that gets men thinking about their health is good," he said.
Contact Weintraub at kweintraub@usatoday.com
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
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