Image Credit: Boston Globe / Contributor / Getty Images 
Welcome to another essay on some of the major themes of my new book, The Last Men: Liberalism and the Death of Masculinity, which explores the social, biological and political implications of rapid testosterone decline in the Western world.
The Massachusetts Male Aging Study—often referred to as the “MMAS” for short—is one of the most important studies for understanding what’s happening to testosterone today across the Western world.
The MMAS was a large-scale, longitudinal, population-based cohort study of men from the Boston area. In simple terms, a large number of men were selected at random from the general population around Boston, and their health was tracked in various different ways over a long period of time.
Just over 1700 men aged between 40 and 70 were selected, and baseline data were collected between 1987 and 1989. Follow-ups took place between 1995 and 1997, and again between 2002 and 2004.
The study wasn’t an intervention study or clinical trial. The men weren’t administered drugs, and they didn’t change their diet or lifestyle. Instead, they were monitored through a battery of tests: They completed interviews at home, filled out questionnaires on their health, lifestyle and sexual function, and they provided blood samples, so their hormone levels could be measured and compared over time.
The study was groundbreaking for a number of reasons, not least of all because of its scale. Never before had there been a study of male sexual and hormonal health that took such a large number of subjects at random, followed them for so long, and produced robust evidence that could be generalised for the rest of the male population (i.e. of the entire US).
Among other things, the study established prevalence and incidence figures for conditions like erectile dysfunction; helped provide reference ranges for various hormones in men, including testosterone; revealed risk factors for decline in those hormones, such as smoking and being overweight; and led to the notion of an “andropause”—or late-onset hypogonadism, to use its technical name—a condition in which hormones like testosterone decline and reach low levels as a result of aging and related factors.
Papers based on the MMAS are among the most cited of all scientific papers. One paper on erectile dysfunction has 7,500 citations and counting.
The study’s findings with regard to testosterone have proven hugely influential. As well as finding correlations between reduced testosterone and factors like obesity, diet and physical fitness, the study revealed significant cross-sectional and longitudinal declines in testosterone between the beginning and end of the study. Again, to simplify, the study showed that not only does testosterone appear to decline with age (that’s the cross-sectional decline), but testosterone levels have been declining in general with the passage of time as well (that’s the longitudinal decline).
Here’s an example to illustrate what that means. A man who is 30 will have more testosterone than a man of 70 at any point during the study, but a man of 30 at a later point in the study will have less testosterone than a man of 30 at an earlier point.
Within a man’s lifetime, the study showed, he can expect to lose around 1% of total testosterone each year, and 2% of bioavailable testosterone—testosterone the body can use.
Total testosterone, at the population level, declined 1.6% year on year, and bioavailable testosterone declined as much as 3%.
It was this second decline—the longitudinal decline—that got researchers worried. Over a period of just 15 years, testosterone levels declined 20%, and further analysis showed that the decline could not be explained by factors like changing rates of obesity, smoking or other health factors captured by the study. Something else was to blame, like growing exposure to hormone-disrupting chemicals, otherwise known as endocrine-disruptors, but the researchers couldn’t say exactly what.
The findings of the MMAS inform virtually all serious discussions of male sexual health that have taken place since. They’re central to my new book, The Last Men: Liberalism and the Death of Masculinity, but they’ve also informed many other scientific studies, a number of which have corroborated the central finding of a population-wide decline in testosterone.
This decline has been corroborated not just in America, but also in Europe and elsewhere in the Western world: for example, a study of US Air Force veterans for the period 1982-2002;
a Danish population survey for the period 1982-2001; and a massive Israeli survey of 9,000 men between 2006 and 2019.
A more recent American study has shown the decline is also taking place among adolescents and younger men. Between the ages of 15 and 39, a decline of 25% over 16 years was found. The decline held up even after we adjustment for factors like obesity, suggesting again that something else was to blame.
It’s imperative we find out what, and do something about it.
