The standard narrative is that testosterone levels peak in a man’s early 20s and then decline throughout the rest of his life. This is associated with a general worsening of health due to the aging process. Moreover, the decline of testosterone is seen as another inevitable facet of the aging process. However, many things change with age, such as BMI. But, we do not say being old causes weight gain.
Testosterone Decline in Western Populations
If we are talking about the general western population, then testosterone does decline with age.
Several large cross-sectional studies have come to consensus on a 1–2% annual decline in free or bioavailable testosterone, offset by a rise in SHBG, resulting in a net decline in total testosterone. (1)
These studies were mostly conducted in the US, with others done in France and Denmark. In addition over the last 40 years, there has been a generational decline in testosterone and sperm quality in western men.
Testosterone Decline Worldwide
In contrast, when we look worldwide the decline seems much less certain. The table below shows a 29% decline in the US, 14% in Congo, 10% in Nepal, 3% in Paraguay (2).
The Congolese men were horticulturalists from the Ituri Forest, the Nepalese were agropastoralists from central Nepal and the Paraguayans were from the Ache hunter-gatherer tribe. These 3 groups are relatively isolated from the modern world and its influences. They are living a traditional lifestyle, one that their ancestors would have lived for many generations. In contrast, the American men from Massachusetts would have been living a modern western lifestyle.
We can see that the decline in the hunter-gatherer group (Paraguay) is almost non-existent and in groups on traditional agricultural diets (Congo, Nepal) there is only a slight decline. Whereas, there is a steep decline in men living a modern lifestyle (USA), which is consistent with other western studies.
Furthermore, a study measuring testosterone levels in men from the Kung tribe, a hunter-gatherer group in Namibia. Observed that:
[testosterone levels decreased] with increasing supplement of the traditional hunter‐gatherer diet with domestic and Western food products (3)
Does a High Testosterone Level In The West, Mean More Decline?
If you look at the table again (in the previous section), you can see that the American men had the highest testosterone and most decline. And, that the Paraguayan men had the lowest testosterone and the least decline. The Nepalese and Congolese men fit into the middle of this pattern. The authors suggested that the Western men experienced the most decline due to their high starting levels. This would mean that the age-related decline in western testosterone levels is no big deal.
However, the table shows that US men aged 45-60 had lower testosterone levels than Congolese men aged 45-60. Despite starting at much higher levels. Moreover, the Congolese men had recently experienced a food shortage which would have suppressed their testosterone levels (4). Meaning, normally the Congolese men would have had a higher testosterone level, which would make the US 45-60 group look even lower.
Furthermore, the US subjects were recruited by a newspaper ad, which may have caused selection bias. The ad may have discouraged lower testosterone men from participating due to fear of embarrassment or anxiety over the results. In contrast, higher testosterone men may have had more confidence to participate, as testosterone increases confidence (5). Therefore, the sample would be skewed towards higher testosterone men, rather than average men.
Ethnic Differences in Testosterone Levels
Finally, the differences in youthful testosterone levels may be due to genetic or geographical differences. Testosterone does vary by ethnicity (6), and therefore lower starting levels of non-western groups could be due to genetic differences. Consequently, the large decline of the testosterone in Massachusett’s men would still be seen as a pathology.
Healthy Western Men Have High Testosterone
High testosterone levels are good for you and are a general indicator of good health. Men who have high testosterone have a reduced risk of cardiovascular disease (7) and most importantly reduced all-cause mortality (8).
An Australian study found no correlation between age and testosterone levels, in men reporting very good or excellent health (9). The men also had rates of obesity and hypertension lower than those in the general population. Moreover, BMI and ex-smoker status was found to negatively correlate with testosterone. Overall, this study shows that a decline in testosterone is due to age-related pathologies such as an increasing BMI, and not an inevitable consequence of aging itself.
High Testosterone Does Not Causes Prostate Cancer
The most recent meta-analysis on the subject concluded:
Prostate cancer appears to be unrelated to endogenous [natural] testosterone levels. Testosterone replacement therapy for symptomatic hypogonadism does not appear to increase prostate specific antigen levels nor the risk of prostate cancer development. (10)
The researchers found that naturally high testosterone levels were not associated with prostate cancer. And that, testosterone replacement therapy was also not associated with prostate cancer.
- In the average western man testosterone declines with age.
- However, in men living a traditional agricultural or hunter-gatherer lifestyle, less decline is seen.
- Western men who are in very good health do not see a decline in their testosterone.
- High testosterone makes men live longer and have a reduced risk of disease.
- The decline of testosterone in western populations is because older men tend to become less healthy, such as they gain weight.
- Low testosterone levels are not an inevitable part of the aging process.