Declining Sperm Counts Worldwide

During the nearly 2 decades that I have been a physician, I have come across numerous scientific articles and seen many news headlines suggesting that sperm counts across the world appear to be declining.  These studies were always accompanied by caveats, though, and frequently presented conflicting data.  My hope has always been that the alarming findings of these studies were the result of sampling bias or statistical errors, and did not truly represent a progressive decrease in actual sperm counts among the world’s population.

Unfortunately, that optimistic thinking was upended by a recent article published in the journal Human Reproduction Update by H. Levine, et al.  The investigators in this article went back and evaluated 185 studies from around the world looking at semen analysis testing between 1973 and 2011 in 42,935 men.  The results were not reassuring for those living in so-called “Western” regions, including North America, Europe, and Australia/New Zealand.

The Levine study found that over the past 4 decades, average sperm density (millions of sperm/cc) in men living in these Western regions dropped by 52.4%, while the total sperm counts (total number of sperm in the entire ejaculate) dropped by 59.3%.  This equated to a 1.6% drop in the total sperm count of men each year of the time period studied.  Even more alarming was the fact that this progressive decline appears to be continuing with no sign of levelling off in the more recent years that were studied.  Interestingly, studies from men in South America, Africa, and Asia did not show any significant decreases in sperm counts over the past 4 decades, though it is worth noting that studies from these regions were less numerous and therefore had less statistical power.

So what to make of these findings?  What is now clear is that the progressive decline in sperm counts in men from Westernized countries does appear to be a real phenomenon.  Many possible explanations have been hypothesized as contributors to decreasing sperm production in the general population.  These include increasing environmental exposure to “endocrine disruptors”, such as Bisphenol-A (or BPA, which continues to be used commonly in everyday objects such as water bottles), phthalates (used as plasticizers to soften hard plastics such as PVC), air pollution, and pesticides.  Increasing levels of obesity, diabetes, and the more sedentary lifestyle of modern society have also been cited as likely contributors to decreasing sperm counts.

The normal male body has a built-in fertility “reserve” whereby it normally produces more sperm than is actually necessary for procreation.  This extra reserve of sperm has so far kept population fertility rates fairly steady despite 4 decades of progressive decreases in sperm numbers.  However, if trends do not change, then there will eventually be a “tipping point” where decreasing sperm counts will reach a level in which the ability to effectively and efficiently establish a pregnancy will be increasingly impaired.  In addition to the fertility concerns, lower sperm counts also tend to be correlated with an increased risk of other health-related problems, such as undescended testicles at birth, testicular cancer, and hypospadias (where the male urethral opening is not located in its normal position at the tip of the penis).

Clearly, more research is urgently needed to help determine exactly which risk factors are contributing the most to the progressive decline in sperm counts in men from Western countries.  We can no longer rely on optimistic thinking- the decline appears to be real, so it is time to take action.