Concerned scientists say the sperm count of men in Western nations has dropped significantly since the 1970s, a change that may signify underlying public health issues. They described their findings in the journal Human Reproductive Update.

The international team of researchers analyzed data from 185 studies of semen samples collected from 1973 to 2011. The 42,935 donors hailed from 50 countries, which the scientists divided into two groups: "Western," including North America, Europe, Australia, and New Zealand; and "Other," including South America, Asia, and Africa.

At first glance, the results are both concerning and surprising. The last 40 years seem to have seen a slow but significant sperm slump among American and other Western men. The studies recorded an average annual decrease of 1.6 percent, yielding a total loss of 59.3 percent over the 38-year study period.

The same could not be said for men in the "Other" group, whose sperm count appeared to experience no significant change.

The authors of the current paper seem alarmed by their own findings.

"The fact that the decline is seen in Western countries strongly suggests that chemicals in commerce are playing a causal role in this trend," co-author Shanna Swan of the Icahn School of Medicine at Mount Sinai told New Scientist.

Swan and her colleagues did not look into any possible causes of the decrease but believe it could be a sign of overall declining health in the West.

"A decline in sperm count might be considered as a 'canary in the coal mine' for male health across the lifespan," they write. "Our report of a continuing and robust decline should, therefore, trigger research into its causes, aiming for prevention."

But before we all freak out, it's important to consider other elements that could be influencing these results. First, the sperm samples were not distributed evenly across all 50 nations. Only 16 percent of samples came from North America, and there were far fewer studies on the "Other" group overall; it's possible that sperm populations in South America, Asia, and Africa are experiencing the same slow decline.

Second, these studies measured sperm count—not sperm quality.

Third, and most importantly, even with the decrease, the global average sperm count remains within normal range. While a downturn means that more men's count may fall beneath ideal levels, we’re hardly facing a worldwide sperm shortage. Let's take this situation one drop at a time.