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Page 2 of 4
Bad News for All of Us
The cross-sectional results looked at all the subjects during the same time period. The data was grouped by the year the blood sample was taken and the comparisons were made by age for all the subjects for that time period. Thus, the 1987-1989 results of all subjects were compared, then the 1995-1997 results, and finally, the 2002-2004 time period. This allowed the scientists to look at the changes in testosterone concentrations due to age (how old the subject was at the time). In all three time periods, a clear decline in testosterone concentrations was present as the age of the subjects increased.1 In other words, the testosterone concentration of 45-year-old men was greater than 55-year-old men, which was greater than 65-year-old men, and so on.
The cross-sectional decline in testosterone concentration was 0.4 percent per year of age, which means that if two groups of men of different ages have their blood drawn at the same time, the older men’s testosterone concentrations will be lower by a factor of 0.4 percent times the age difference.1
The article demonstrated this point by discussing two groups in the 1987 group. The older men had a median age of 65 and their average testosterone concentration was 5.5 percent lower than another group of men whose median age in 1987 was 56. Thus, at any given point in time, older men generally have lower testosterone concentrations than younger men— sounds good so far for Generation X.
The next set of analyses looked at changes in the same subject over time, (longitudinal analysis). If today’s 45-year-old has more testosterone than today’s 65-year-old, then it stands to reason that today’s 45-year-old will have less testosterone in 20 years when he’s 65. In fact, this is true and is the recognized, aging-related decline in testosterone concentration, sometimes called andropause.2 The article demonstrated the absolute decrease in testosterone concentration over time by discussing the representative values of one group between T1 (1987-1989) and T2 (1995-1997). The average time span between blood draws was 8.8 years and during this time, the group’s testosterone dropped an average of 16.1 percent. This equates to a longitudinal decline of 1.6 percent per year.1 So, for all healthy men, testosterone concentrations drop rapidly between our mid-50s to mid-60s— bad news for all of us.
So far, we’ve learned that younger men have more testosterone than older men, but we will all eventually become old men with low testosterone if we live long enough. As interesting as that is, it doesn’t directly answer the burning question of which generation could be considered the manliest?
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Research and Review 
