Hormonal
American men have experienced a substantial, age-independent population-level decline in serum testosterone concentrations between 1987 and 2004, independent of chronological aging.
This research indicates that the average American man today has lower testosterone levels than his counterpart from 20 years ago, even at the same age. This decline is not explained by common lifestyle factors like obesity or smoking. While you cannot change your birth cohort, this highlights the importance of monitoring hormonal health and investigating potential environmental or lifestyle factors that may contribute to this secular trend.
We observe a substantial age-independent decline in T that does not appear to be attributable to observed changes in explanatory factors, including health and lifestyle characteristics such as smoking and obesity.
Why this rating
Large prospective cohort study (MMAS) with multiple waves over nearly 20 years, rigorous statistical controls, and consistent results across total and bioavailable testosterone.
Source
A Population-Level Decline in Serum Testosterone Levels in American Men
Thomas G. Travison et al. · The Journal of Clinical Endocrinology & Metabolism · 2006
DOI 10.1210/jc.2006-1375
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