Sperm counts are falling precipitously across the rich world

IN STANLEY KUBRICK’S film “Dr. Strangelove”, set during the Cold War, an American air-force general orders a retaliatory nuclear strike against the Soviet Union. It is later revealed that the Soviets did not attack first. Instead the commander, who had a mental breakdown, ordered the strike because he had become convinced that communists had fluoridated America’s water supply in an effort to damage the “precious bodily fluids” of America’s men.

The paranoid commander’s fears about his fertility were easy to mock in 1964, when Kubrick’s film was first released. But the premise may be getting closer to reality with each passing day. In 2017, Shanna Swan of the Mount Sinai School of Medicine in New York and Hagai Levine of Hadassah-Hebrew University in Jerusalem, along with six other researchers, estimated the average sperm count for 43,000 men in 55 countries across the world. The data, from 185 previously published studies, suggest that sperm counts fell by about 25% between 1973 and 2011 (see chart). But the academics performed a regression analysis that controlled for variation in the studies' sampling technique, their potential sample bias, the age of men and their level of abstinence before a sample was taken. They found that sperm counts had in fact fallen by about 50% in Western countries over the period. Although the data were less plentiful, similar trends were observed in developing countries, too.