The swimmers are going missing — and no one knows why.
185 studies reveal men's sperm count has plunged worldwide over the last 40 years
A massive new analysis of prior research has found steep declines in male sperm count over the last several decades.
According to an analysis of 185 academic studies, sperm counts around the world have been declining steadily over the last four decades, such that today's counts are roughly half of what they were 40 years ago, the BBC reports.
Between 1973 and 2011, sperm counts declined 59.3% "with no evidence of a 'leveling off' in recent years," investigators from multiple international universities wrote in their report.
These declines imply that a growing proportion of men have sperm counts below the thresholds for reduced fertility or full-fledged infertility, the researchers noted. This could mean a few things in a broader sense.
Demographic experts have observed for close to two decades that developed countries are increasingly seeing falling fertility rates. (In Japan, the population is actually decreasing.) Gender equality has encouraged more women to enter the workforce, despite a laggard set of policies at many employers that don't accommodate both work and family life.
The latest findings add to that story of falling fertility by including biological reasons that couples aren't having nearly as many children as they used to.