August 18th, 2011
07:30 AM ET
Didn’t men use to be more masculine? They were more ready to fight back, right? They walked with more swagger, and just did more things their way.
Researchers can’t measure swagger – but they can measure testosterone, the male sex hormone most responsible for masculine behaviors – and studies show that testosterone levels in men have been on the decline for decades.
Two major studies have confirmed the phenomenon, one in U.S. men and another in Danish men. In the U.S. study, the total testosterone levels measured in men’s blood dropped approximately 22% between 1987 and 2004.
Of course testosterone levels drop as men get older, but what makes the study shocking is that men today actually have less testosterone than men used to have at the same age.
The challenges to men’s health may not be limited to testosterone levels. The amount of sperm in ejaculated semen may be falling too.
A 1992 Danish analysis of sperm quality from other studies concluded that sperm quality has been dropping for decades, and a 1997 reanalysis using different mathematical modeling confirmed the decline, estimating a drop in sperm levels of about 1.5% per year in the United States.
But researchers have been gathering new data since 1996, this time using semen from Danish 18-year olds testing for military service.
That data shows no such decline at all. Oddly, the results have not been published in a peer-reviewed journal, but were instead released early to the Danish government, which then published them online.
If there’s strong evidence that testosterone is dropping, and the jury is still out on the decline of sperm, what other health challenges are men facing?
Male sex organ malformations are certainly among them. Hypospadias for example, a condition in which the man’s urethra opens somewhere before the tip of the penis, nearly doubled in prevalence from 1970 to 1993 according to national Birth Defects Monitoring Program.
Another study found that the percentage of babies in neonatal intensive care units with hypospadias jumped from just .4% in 1987 to 4% in 2000.
Boys also suffer higher rates of once-rare disorders like ADHD and autism. A comprehensive study of South Korean schoolchildren published earlier this year estimates 3.74% of all boys in that country have some form of autism, compared to 1.74% of girls.
To top it all off: there’s evidence that the percentage of babies born male is declining.
In the general population the difference is slight, but statistically relevant. One group of epidemiologists found that in the United States, the percentage of Caucasian babies born male decreased from 51.43% in 1970 to 51.22% in 2002. That’s equivalent to about 21 fewer men per 10,000 births.
In some populations, the drop is far more significant.
A group of Native Americans – the Chippewas of Aamjiwnaang – live on a reserve surrounded by large industrial chemical plants in Ontario, Canada. The percentage of male births there dropped from a normal rate of 55.1% in the years 1989-1993 to just 34.8% in the years 1999-2003.
Why is this happening?
Many researchers cited here mention changes in our environment, like an increase in the number of chemicals we’re exposed to in the womb, and throughout life.
Precisely how it all happens though is somewhat outside our scientific understanding, and of course something like testosterone levels affects each man very differently.
“Two men of the same age may have exactly the same testosterone level but feel very different physically, emotionally, and sexually,” says Ian Kerner, CNN’s sex counselor. “I try to work with men to re-define sex in a way that works with their situation.”
What is clear is that for whatever reason – men are taking some big biological punches from modern life.
About this blog
Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.