New research suggests there has been a significant drop in sperm counts among men in western countries.

The research, billed as the first systemic review of sperm count trends around the world, found a 59.3% drop in sperm counts in North America, Europe, Australia and New Zealand between 1973 and 2011.

Over the same period there was also a 52.4% decline in overall sperm concentration in the West.

The study also indicated that the rate of decline has shown no sign of slowing.

While the study does not suggest any explanation for the decline, falling sperm counts have long been linked to lifestyle factors – as well as exposure to certain chemicals and pesticides.

General Practitioner, Dr Monah Mansoori said smoking, drinking and obesity are prime suspects:

“We are always talking about the ticking time clock for women and ‘don’t leave it too late’ that sort of thing,” she said.

“But actually we do need to think about it for men as well and I think anyone who is thinking of starting a family needs to be aware of the factors that will affect their sperm count.”

Dr Shanna H Swan, who took part in the study, said the fact that the decline is seen in western countries “strongly suggests that chemicals in commerce are playing a causal role in this trend."

Her colleague – and lead author of the study – Dr Hagai Levine said the research should provide an urgent wake-up-call for health authorities around the world.

Systematic review

Researchers in The US and Israel screened 7,500 studies – and performed analysis on nearly 200 more – to arrive at their conclusions.

While the drop was recorded in the west, there was no significant change in the rest of the world.

Researchers warned that there have been far less studies undertaken in South America, Asia and Africa – potentially skewing the results.