February 24, 2024

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Stanford: The human penis length has increased 24% in 30 years

Stanford: The human penis length has increased 24% in 30 years


Stanford: The human penis length has increased 24% in 30 years but it is not a good thing.



On February 14, the “World Men’s Health Magazine” published an article and concluded that compared with 30 years ago, the average length of males around the world has increased by 24%, reaching about 13.93 centimeters.

Big and long is the obsession of men. For this reason, some people have used knives, some have taken medicine, and some have hung bricks.

Now, do nothing and become longer (cháng) ? Sounds like good news.


The corresponding author of the study, Michael Eisenberg , a professor of urology at the Stanford University School of Medicine, is worried: “The sperm count and testosterone level of modern men have been declining, and the risk of testicular tumors and congenital developmental defects The incidence is also increasing.

It was thought that men might become ‘shorter’ and less fertile.” However, the results of the study were not the same.


When something goes wrong, there must be a demon. Michael Eisenberg said that changes in body anatomy, such as the length of male genitalia, are one of the most important topics in human biology. Growing so fast could mean that the body is undergoing some major changes, “not necessarily a good thing . “



Different lengths in Different regions

Male fertility and sexual dysfunction are the research directions of Michael Eisenberg.

He found that as life circumstances changed, discussions about male reproductive health continued to emerge.

However, few people have systematically meta-analyzed the changing trends of male body anatomy in different regions and in different periods.


Therefore, he teamed up with scholars from the San Rafael Scientific Research Hospital in Italy, the San Rafael University of Life and Health, and the Rollins School of Public Health at Emory University in the United States to collect data from multiple databases from 1942 to 2021.

A collection of 75 studies of male penises involving 55,761 men over the age of 17.


There are two main findings of this meta-analysis.


First, different regions have different lengths.


The results show that in the natural (relaxed) state, the average length of the male root is 8.70 cm (95% CI, 8.16-9.23) ; when stretched, it is 12.93 cm (95% CI, 12.48-13.39) ; after erection, it can reach 13.93 cm (95%CI, 13.20-14.65) . The upright posture is used for measurement, and the length calculation method starts from the pubic bone at the root of the penis and ends at the urethral opening at the head of the penis.


The study found regional differences in the length of the male root. More than 50,000 men came from all continents of the world. Include 20 relevant studies in Asia, including at least two studies in China. The penises of African men are generally shorter than those of European and North American men. When it comes to specific usage scenarios, African men surpassed Europe and the United States with an average of 14.88 cm, but lost to Oceania (15.71 cm) . The average number of Asian men in any of the above states does not reach the world average.



Stanford: The human penis length has increased 24% in 30 years

The measurement results of people in different periods, different regions, and different population characteristics in different states. (Photo source/WJMH)


Second, the length has changed in different times.

After adjusting the age and demographic characteristics of the subjects, the study found that the length of the global penile erection has increased significantly over time (QM=4.49, df=2, p=0.04) .

“In the past 29 years, the erect penis has increased from an average of 12.1 cm to 15.2 cm.” Michael Eisenberg explained that this change was not observed in the “natural” and “stretched” states .




After a long time, why is it a bad thing?


“Overall, the research conclusions are contrary to our original design intentions.” Michael Eisenberg said in an interview with Stanford Medical School.

He said that in recent years, there has been a lot of bad news in male reproduction research.

At the end of 2022, a study found that since the 1970s, the average sperm count of men has almost halved. During the same period, congenital developmental abnormalities such as cryptorchidism and hypospadias tended to increase, especially the incidence of severe hypospadias increased.

This may be due to the wide application of pesticides, plasticizers, etc., resulting in an increase in environmental estrogen-like substances. Earlier research suggested that environmental pollution may also cause the penis to “shrink”.


Environmental pollution, sedentary and junk food are factors that lead to obesity. In June 2022, the “Asian Journal of Andrology” published a French multi-center study and found that obese men have a higher risk of sperm DNA damage, which may affect conception, embryo and blastocyst development, and increase the risk of miscarriage. Infertile men also generally have shorter external genitalia than healthy men.


In view of the development trend of the general environment, Michael Eisenberg and others once believed that the general “negative growth” of the penis may be seen in the male group.


In the face of the existing data, Michael Eisenberg said that we should remain vigilant. The length of the penis is an important feature of the reproductive system, which is related to endocrine and reproductive hormones.

There are many endocrine-affecting chemical substances in the diet and environment, which may cause the developmental age to be advanced and the entire developmental period to last longer, or cause changes in the average penis length.


He pointed out that the next step should be to strengthen relevant research, verify the above findings, and explore the reasons and risks.

In addition, similar studies should be conducted in pediatric patient populations and in women. Checking penis length may be included in child care, just like measuring children’s height and weight every year.

This should probably be considered an early indicator of changes in human physical development.


Long ≠ strong


James M. Hotaling, a urologist and male infertility specialist at the University of Utah School of Medicine, was not involved in the study. He doesn’t think it’s hard to explain the differences in the measurements. It may be that the measurement methods have changed over the past few decades.


Some Australian scholars said that there is “bias” in the research data, which may also be related to the subjects. “Shorter, smaller men may refuse to participate in these types of studies.”


Michael Eisenberg and others also stated in the article that there are shortcomings in the measurement method. For example, temperature, waking state, body size, researcher factors, etc. were not ruled out.


However some experts also think that the root cause of the change in penile erect length has not yet been determined, nor can it be said that it has a negative impact on reproductive function. If it is really caused by negative factors such as lifestyle, obesity, hormone disruptors, and environmental factors, as assumed in the article, it may be detrimental to reproductive function.


In the past, many people thought that longer genitalia = better development = stronger ability.

This is just a man’s self-feeling, not medically. “Excluding dysplasia caused by diseases, there is no direct relationship between the length of a normally developed penis and sexual function and fertility.”


[1]Worldwide Temporal Trends in Penile Length:A Systematic Review and Meta-Analysis.World J Mens Health.2023;41:e31.doi.org/10.5534/wjmh.220203
[2]Is an increase in pencil length cause for concern?.Standford Medicine
[3] Men’s health: Penis length has grown 24% in recent decades. That may not be good news. USA Today

Stanford: The human penis length has increased 24% in 30 years

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