My belief is that the primary cause is environmental chemicals, specifically Phthalates and BPA (and related chemicals). The science on this is fairly conclusive. We can show that these chemicals bind to estrogen receptors, that they're present in everyone's body, and that if you're acutely exposed to a higher dose, your testosterone goes down. In my opinion, these chemicals are having social and cultural effects beyond sperm counts. As individuals, there are some things you can do, but some studies have shown that about the best you can do with personal actions is a 50% reduction. The most effective things are to try not to handle store receipts on thermal paper, and wash your hands after you do, and avoid anything that has been microwaved in plastic. Generally reducing heavily processed and fast food is next, because you can't know about things like ingredients flowing through PVC tubing that leaches Phthalates.<p>Ultimately we are in dire need of regulation of these substances, especially where there is food contact. I'm not very optimistic under trump. Someone clever though might be able to come up with a campaign about chemicals stealing your manhood that might resonate with conservative voters.
People offering human-centric explanations like cell phones: Note also that the sperm quality of dogs has decreased 30% since 1988.<p><a href="https://elpais.com/elpais/2016/08/09/ciencia/1470755907_243246.html?rel=mas" rel="nofollow">https://elpais.com/elpais/2016/08/09/ciencia/1470755907_2432...</a><p><a href="https://www.nature.com/articles/srep31281" rel="nofollow">https://www.nature.com/articles/srep31281</a><p>This suggests its more environmental, chemical, diet-based, etc.
Unless this is adjusted for activity levels (western folks are <i>extremely sedentary</i> - especially in the US) and weight I am not sure it is interesting. Obesity is negatively correlated with male fertility[1] and 3/4 of the US is obese or overweight[2].<p>[1] <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3521747/" rel="nofollow">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3521747/</a><p>[2] <a href="https://www.niddk.nih.gov/health-information/health-statistics/overweight-obesity" rel="nofollow">https://www.niddk.nih.gov/health-information/health-statisti...</a>
I've personally become concerned recently with the abundance of BPA and it's effect on the endocrine system of men. Between disposable water bottles, aluminum can liners, and food stored in plastic containers, there's a huge amount of exposure to this endocrine disruptor. The article doesn't mention it in particular, but I think it's worth being cautious over.
Are cell phones in our pockets to blame? The effects of radiofrequency electromagnetic radiation on sperm function. – <a href="https://www.ncbi.nlm.nih.gov/pubmed/27601711" rel="nofollow">https://www.ncbi.nlm.nih.gov/pubmed/27601711</a><p>More info here: <a href="https://www.ncbi.nlm.nih.gov/pubmed/27076112" rel="nofollow">https://www.ncbi.nlm.nih.gov/pubmed/27076112</a><p>Also here: <a href="https://www.ncbi.nlm.nih.gov/pubmed/26949865" rel="nofollow">https://www.ncbi.nlm.nih.gov/pubmed/26949865</a><p>And here: <a href="https://www.ncbi.nlm.nih.gov/pubmed/26206279" rel="nofollow">https://www.ncbi.nlm.nih.gov/pubmed/26206279</a><p>Here too: <a href="https://www.ncbi.nlm.nih.gov/pubmed/24982785" rel="nofollow">https://www.ncbi.nlm.nih.gov/pubmed/24982785</a><p>More fuel for the fire: <a href="https://www.ncbi.nlm.nih.gov/pubmed/24927498" rel="nofollow">https://www.ncbi.nlm.nih.gov/pubmed/24927498</a>
It's tempting to decry how we've disrupted the environment in which we live. (Apparently, since there are roughly 200 comments on that theme...)<p>A more interesting potential cause of the sperm drop would be the human environment changing in a <i>beneficial</i> way. That is, it might be that sperm production is negatively correlated with other competitive traits. If that were the case, then we would expect the availability of modern medicine to drive a reduction in sperm count, as competitive-but-previously-infertile individuals are now better able to reproduce. After all humans are a K-selected species.<p>Of course this is silly, because not enough time has passed for these effects to emerge in the human population. However, we do see these effects in livestock. Thoroughbred horses released into the wild would quickly die off, since female fertility has dropped precipitously in a breeding context of "if the mare runs fast enough, we'll spare no expense getting her pregnant".
It would be interesting to see a study that compares the drop in sperm count to the drop in testosterone, to see if the drop is statistically significant or just a symptom of the drop in testosterone.
Turns out modernity is an extremely unhealthy environment for humans, especially men. Despite the narratives being thrown at you, we live in an incredibly "feminized" society where social stigma/violence/shaming are more powerful for the average person than plain old physical violence.
Why not just compensate by ejaculating more often?<p><a href="https://www.youtube.com/watch?v=fUspLVStPbk" rel="nofollow">https://www.youtube.com/watch?v=fUspLVStPbk</a>
it is biologically connected and nicely correlates with the falling testosterone levels. In addition to environmental chemicals, testosterone levels are very significantly affected by behavioral/social factors. Given that society becoming more civil is at the same time a result and a cause of lowering testosterone levels, i think that despite temporary setbacks, like the recent success of the "Make the sperm count great again" campaign, the writing is on the wall here. Anyway, given the power of current and future technology, the count of 1 is enough, and may be even that would become too unnecessary big.
its the drugs in our drinking water : <a href="http://mobile.nytimes.com/2007/04/03/health/03iht-snwater.1.5126782.html" rel="nofollow">http://mobile.nytimes.com/2007/04/03/health/03iht-snwater.1....</a>
This <i>could</i> be due to population size. Isn't there a species of fish where a male becomes a female when there are no other females left? It seems plausible that some mechanism is in place to self regulate.
I think it's simple: fat unhealthy men have lower sperm counts and America has way more fat unhealthy men over the last 40 years. Doesn't look like the meta analysis dealt with this.