Sexual Health

While recent research has shown that average sperm counts and testosterone levels have been in decline for men over the past few decades, erect penile length has surprisingly been trending in the opposite direction, according to a new global study.

A team led by Michael L. Eisenberg, MD, the director of male reproductive medicine and surgery and a urology professor at Stanford University School of Medicine in California, analyzed penis measurements from 75 studies conducted between 1942 and 2021, which recorded this anatomical data from more than 55,000 men ages 18 to 86.
In the context of studies that have found decreasing sperm counts and testosterone levels, “We expected that we would see a similar declining trend when we looked at penile length,” says Dr. Eisenberg, who is also a specialist in male sexual function, “but we found quite the opposite.”

Researchers looked at 20 Studies Involving 18,000 Males

The results, published on February 14 in the World Journal of Men’s Health, identified an increase of 24 percent in the average erect penis length between 1992 (when the first erect lengths were recorded) and 2021. The change over those 29 years increased from an average of 4.8 inches to an average of 6 inches. The calculations were determined from 20 studies that recorded those measures in more than 18,000 males in that time period.

The pooled data also included measures for flaccid length and stretched length (a way to estimate erect penile length). All measures included were conducted by investigators and none were self-reported. The study team noted that erect length increased significantly over time in several regions of the world and across all age groups, while no trends were identified in other penile size measurements.

Eisenberg suggested that stretch lengths did not follow the same trend as erect lengths because there were differences in how measurements were taken, including how hard a clinician pulled for measuring. Techniques for measuring erect penises, however, appeared quite consistent.

Environmental Factors May Play a Role in Increasing Penis Lengths

“Our reproductive system is one of the most important pieces of human biology. If we’re seeing this fast of a change, it means that something powerful is happening to our bodies,” says Eisenberg. “We should try to confirm these findings and if confirmed, we must determine the cause of these changes.”

He suggested that a number of environmental factors may be involved, such as exposure to hormone-disrupting chemicals in our surroundings (pesticides, for example). Some research has indicated that chemical exposure may be linked to boys and girls going into puberty earlier, which may affect genital development, according to Eisenberg.
He added that research has found an association between early pubertal timing and high rates of obesity and sedentary behavior, so that may be a driver behind the trend as well.

Could the Rise of the Internet Have Played a Part?
Larry Lipshultz, MD, the chief of the Scott Department of Urology's Division of Male Reproductive Medicine and Surgery at Baylor College of Medicine in Texas, who was not involved in the study, found the results surprising given that most environmental and lifestyle factors seem to inhibit reproductive health.
He did propose, however, that the advent of the internet, starting in the mid-1980s, could possibly have played a role.
“You might possibly blame online porn, but that’s just a theory,” says Dr. Lipshultz. “The more someone has erections, there might be greater potential for better erections. The tissue would stretch more, hence would get longer.”
Bigger Is Not Necessarily Better

While some may view an increase in penis length as good news overall, Raevti Bole, MD, a urologist affiliated with the Cleveland Clinic who specializes in male sexual medicine and erectile dysfunction, stresses that people may put too much value on penis size.

“Overall I think the results are good in that they don’t show a deterioration [of the penis] — but at the end of the day penile length is very subjective, and I think there can be a negative to focusing on this,” says Dr. Bole, who was not one of the study researchers. “There’s a real emphasis on size in popular culture and social media, so I think it’s important for doctors to reinforce that bigger is not necessarily better. My point is size doesn’t necessarily correlate to sexual satisfaction. Patients can feel bad about penis size, and that’s a problem.”

More Research Is Needed

The next big step in terms of research for Eisenberg is to look at other patient populations (such as children and adolescents) to see if there are similar changes, because it may turn out to be an early indicator of a change in human development.

“Also, if there’s granular data on lifestyle factors or environmental exposures, we could try to understand why this may be happening,” he says.

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