The Sperm-Count ‘Crisis’ Doesn’t Add Up

Reports of a decline in male fertility rely on flawed assumptions, a new study contends.

Male scientists have long waxed poetic on the contents of their testes. “Sperm is a drop of brain,” wrote the ancient Greek writer Diogenes Laërtius. Leonardo da Vinci drew the penis with a sperm duct that connected directly to the spinal cord. The 17th-century microscopist Antonie van Leeuwenhoek claimed that each sperm cell contained within it a folded-up human being waiting patiently to unfurl. For nearly as long, scientists have fretted about sperm’s seemingly inevitable decline. Most recently, a series of alarming headlines — as well as a new book by an epidemiologist at Mount Sinai Medical Center in New York — warned that falling sperm counts might threaten the future of the human race. “It’s a global existential crisis,” said Shanna H. Swan, author of the book “Count Down.” Most of these headlines can be traced to an influential 2017 meta-analysis by Dr. Swan and others, which found that sperm counts in Europe, North America, Australia and New Zealand had plummeted by nearly 60 percent since 1973. The authors screened 7,500 sperm-count studies from around the world, weeded out most of them and ultimately analyzed 185 studies on 43,000 men worldwide.