Like monsoon season, this storm surfaces every several years, and has for decades. And it does so with seemingly undiminished intensity. Human sperm counts are falling, and we are headed for extinction.
The latest published report came in the form of a meta-regression analysis, the latest, uber version of the ordinary meta-analysis, filled to the brim with enough pithy statistics to boggle your mind. It reviewed and summarized the findings from 185 previous worldwide studies of 49,000 patients from 1973-2011. Unfortunately, none of the analyzed data was new. Yep, the same old data, replete with bias and confounders, rehashed anew and jumbled into one mighty “new” paper. It is well done? Yes. In fact, it’s the best you can do given the input. Does it claim anything new? Absolutely not. Just another slightly bigger monsoon.
Sperm Found Down
Yup, in several continents, including North America, Europe and Down Under, the study suggests that sperm counts have fallen by 50-60% over the last 40 years. But on other continents, including South America, Africa and Asia, they have not. So now you know where to move if you want to ensure our survival as a species.
But, lets sort out this “extinction” idea right now. In one analysis from the paper, sperm concentration per ejaculate among Western men decreased from 100 million sperm/mL to 50 million/mL over 40 years. OK, it’s a 50% decrease, but both numbers are well within the range of normal human fertility (>15 million sperm/mL). So, maybe we shouldn’t be throwing around the “extinction” word so quick here as this difference (a) may not be real and (b) may have no material bearing on our fertility potential.
The problem with creating a gorgeous looking house from old materials is that it’s only as good as the blocks from which it’s built. And believe me, when it comes to epidemiologic studies of sperm counts, some of these blocks should not be recycled. Here is a short list of issues that weaken the blocks with unadjustable confounders and biases:
- Semen samples were collected and analyzed in different ways at different times in different studies (method bias).
- More than a single semen analysis is needed to make the man, as semen quality varies by 75% within individuals over time (sampling bias).
- Semen quality also varies by male age and geographic location (age bias).
- Semen quality varies by reason for testing: sperm donors, infertile men, prevasectomy (fertile) men. Because only certain men get sperm counts done, this means the results are not really “generalizable” to the entire population (subject bias).
So what’s a guy to do? The fact of the matter is that we really don’t have the hard facts on sperm counts sorted out yet. And, I would wager that rehashing even more population studies is not necessarily what’s needed going forward. Why not take action now?
The Cure for Humanity
What is clear is that post-industrialized humans are evolving in ways that we could not have predicted even a century ago. Maybe falling sperm counts are of no concern, as women are healthier and more fertile than ever before and (luckily) demand less sperm from us to get the job done. After all, there is no concrete evidence that human fertility potential is changing in developed countries. Or maybe human fertility is genuinely at risk, and we are headed toward The Children of Men scenario. Regardless, instead of worrying about “extinction,” realize that there are things that you can do right now, everyday to affect change: lead a healthy life by treating your body like a temple. And treat the environment with care, leaving this earth a better place than you found it. A better world is best made by better individuals.