Low testosterone is linked to worse health outcomes among older men, especially in the areas of diabetes, dementia and mortality. But the scientific literature is still not clear on whether diminishing levels of testosterone are just due to ageing itself, or if the medical conditions we accumulate as we age contribute to lower testosterone levels. It’s a complex picture because testosterone can vary significantly within and across age groups, so that some older men have testosterone levels similar to younger men.
A new study sought to unravel some of the complexity by examining large volumes of data linking testosterone levels to various health issues at an individual level.
The review analysed data from 11 cohort studies comprising more than 25,000 men. For each study, total testosterone, dihydrotestosterone (DHT) and oestradiol were measured using mass spectrometry. These data were supplemented by lifestyle, health and socio-demographic variables – things like physical activity, education status, BMI, age and alcohol consumption. The data were then put together to determine the relationships between various factors and whether they had an influence on testosterone independent of age.
The researchers found that for men aged 17 and above, average concentrations of testosterone did not change until the man reached 70 years of age, after which testosterone levels tended to drop. This drop even occurred in healthy older men (with no hypertension, diabetes, cancer or cardiovascular disease), although they experienced less of a reduction. High BMI had a major effect on testosterone levels as did diabetes and cancer. There were a host of smaller factors that also influenced testosterone concentrations – such as lower physical activity, high blood pressure, and – interestingly – being married.
Other studies have identified some of these associations before, but this is the first study to do it at scale and using consistent measurements of testosterone. The authors say it’s an important piece of work for understanding how individual men might have varying levels of testosterone based on particular health factors, and how testosterone levels decline – with the potential for treatments if the levels are abnormally low – known as gonadal failure.
Factors associated with circulating sex hormones in men: ACP Journals