This article in the Guardian reported that humans could face a reproductive crisis if action is not taken to tackle a drop in sperm count, researchers have warned after finding the rate of decline is accelerating.

A study published in the journal Human Reproduction Update, based on 153 estimates from men who were probably unaware of their fertility, suggests that the average sperm concentration fell from an estimated 101.2m per ml to 49.0m per ml between 1973 and 2018 – a drop of 51.6%. Total sperm counts fell by 62.3% during the same period.

Research by the same team, reported in 2017, found that sperm concentration had more than halved in the last 40 years. However, at the time a lack of data for other parts of the world meant the findings were focused on a region encompassing Europe, North America and Australia. The latest study includes more recent data from 53 countries.

While it is unclear what might be behind the apparent trend, one hypothesis is that endocrine-disrupting chemicals or other environmental factors may play a role, acting on the foetus in the womb. Experts say factors such as smoking, drinking, obesity and poor diet might also play a role, and that a healthy lifestyle may help to boost sperm counts.