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Sep 2

Fact Check: Have Testosterone Levels Fallen 1% Every Year Since 1980? – Newsweek

The fall of testosterone levels the past several decades has fueled something of a health panic, with public figures and influencers leaning in to share their theories on the phenomena.

Mainstream celebrities, including Tucker Carlson, have examined the claim, in his case also spreading other misinformation by doing so.

Naturally, social media has become a breeding ground for such panic, particularly among platforms skewed to younger audiences, such as Instagram and TikTok.

The Claim

A video posted on August 14, 2022, on Instagram claims that testosterone levels have decreased every year since 1980.

Other videos making the same claim, some of which have hundreds of thousands of views, can also be found on TikTok.

The Facts

The central claim in the video is that testosterone levels have decreased 1 percent every year since 1980. The terms aren't clearly defined, but we can reasonably assume that is a 1 percent reduction per year per male on average for the past 42 years.

This would mean that a male's average testosterone level has fallen 42 percent since 1980.

As it stands, there is very little research to support this specific datapoint.

Studies have indeed shown that testosterone levels have decreased since 1980. Some data shows that mean total testosterone decreased among adolescent and young adult men between 1999 and 2016 by around 25 percent.

A similar study was conducted in 2006, which looked at levels between 1988 and 2003. It found that there had been a decrease of around 15 percent.

Newsweek could not find research that directly compared testosterone levels between men in 1980 and 2022 (raising questions about source for the Instagram claim), but did find one study from 1980 that measured "plasma testosterone levels of sexually functional and dysfunctional men."

Using the mean measurement of testosterone in men with "normal sexual function" in this study and compare it with measurements taken in the 1988-2003 study, data shows a 20 percent increase in the testosterone among the men measured in 1980 versus those measured in 1988.

Combining all of the percentage changes across all the studies mentioned so far would provide you with a figure far beyond the 40 percent mentioned in the Instagram video.

The problem is it's methodologically unsound.

The age, geography, health backgrounds and lifestyle of the men across all the studies would not be controlled in the same way, nor is it likely that the methods used to measure testosterone levels were the same across all the studies.

There may also be other unaccounted variables that could have affected the results. A sum of percentages is therefore not substantive enough to support the Instagram claim.

To explore this in more detail Newsweek spoke to Michael Samoszuk, a Medical Officer at Siemens Healthineers, whose previous work on low testosterone has been published in the International Journal of Impotence Research.

"Analytical methods for measuring testosterone levels have improved considerably over the past 40 years, and it is not advisable to compare "apples to oranges", such as levels measured by older methods to levels measured by contemporary methods," he said.

"Major confounding factors are the selection of the men in such year-over-year comparisons and the time of the specimen collection. Were all of the specimens from 40 years ago drawn from men of the same age and level of health as men from more recent studies? I doubt it.

"Also, the time of collection is very important, because early morning blood draws yield higher levels of testosterone.

"In short, unless the comparative studies are strictly controlled for age, health, and time of blood draw, it is not possible to draw any meaningful conclusions about longitudinal changes in testosterone."

The Instagram video also mentions a number of causes behind the purported decrease in the average testosterone levels, such as consumption of saturated/processed foods and lack of exercise.

According to Dr. Channa Jayasena, a Clinical Senior Lecturer and Consultant in Reproductive Endocrinology and Andrology at Imperial College and Hammersmith Hospital, London, the reason for the decrease has been quite simple.

"Overall levels of testosterone have reduced, but that is only due to increases in obesity and diabetes in the population testosterone is just a marker of a man's health.

"If you take away these factors, it is really uncommon to need testosterone replacement (0.1-2 percent of men, depending on your age).

"So, saying that testosterone levels have reduced over time is like saying that people in Europe became more radioactive in 1986. That may be true, but is misleading since the rise was caused by the Chernobyl nuclear disaster."

The Ruling

Unverified.

There is evidence which shows that average testosterone levels have fallen since the 1980s, but not to the extent that is claimed in the Instagram and TikTok videos. Different studies have charted 15-25 percent decreases between 1980 and 2019, but the results of those studies cannot be cumulatively drawn together.

FACT CHECK BY Newsweek's Fact Check Team

Read the original:
Fact Check: Have Testosterone Levels Fallen 1% Every Year Since 1980? - Newsweek

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