Sperm count in men from North America, Europe, Australia and New Zealand declined by 50-60% between 1973 and 2011, according to a new study from the Hebrew University of Jerusalem. Surprisingly, the study, which analysed data on the sperm counts of 42,935 men, found no decline in sperm counts in men from Asia, Africa and South America, although there was limited data from these areas.

Overall, this is a very disturbing report. There has been a longstanding debate among scientists as to whether sperm counts have decreased or not. But what’s different about this study is the quality of the analysis. It was done in a systematic manner, accounting for several of the problems that had affected previous studies, such as the method used to count sperm and comparing studies performed sometimes decades apart. As such, most experts agree that the data presented is of a high quality and that the conclusions, although alarming, are reliable.

So what is going on? There has been concern for a number of years about an increase in abnormalities in male reproductive health, such as testicular cancer. The decline in sperm counts is consistent with these increases and this adds weight to the concept that male reproductive health is under attack and is declining rapidly.

In fact, if the data on sperm counts is extrapolated to its logical conclusion, men will have little or no reproductive capacity from 2060 onwards. The most rational explanation for the decline in male reproductive health is the changes in the environment. Current research suggests that the male foetus is particularly susceptible to exposure to pollutants and so changes that occur early in foetal life can have a very significant effect on the adult.

What can be done?

The simple answer is that we need much more research to find out why this decline in sperm count is happening. We cannot be complacent about the potential negative effect on fertility and must now urgently rally to substantially increase the research effort into male reproductive health.

Also, although the prevailing evidence shows a decline in reproductive health, not all studies show this; there are some geographical differences. It will be critical to determine what the key differences between geographical regions are – such as genetic differences and exposure to specific pollutants – so we can then examine treatment strategies to limit these negative effects.

If it’s the foetus that is mainly affected, what can the adult man do? Even in adults, exposure to chemicals, such as bisphenol A, which are thought to affect fertility, can have a negative effect, so men should limit their exposure to toxic chemicals. This includes stopping cigarette smoking. Also, a healthy lifestyle is very important as there is a known link between obesity and reduced sperm count.

Chris Barratt, Professor of Reproductive Medicine, University of Dundee.

This article first appeared on The Conversation.