Humans could face extinction if sperm counts continue to drop as fast as they have done in the last four decades in Western countries, a study warns.

Researchers claim the Western lifestyle has more than halved the sperm count of men in the US, Europe and Australia since the 1970s in a new study published by Human Reproduction Update.

Sperm count is the best measure of male fertility, and lead author Dr Hagai Levine said the findings are an 'urgent wake-up call' to investigate lifestyle factors, chemicals and environment that could cause the human species to go extinct.

'If we do not make a drastic change to how we live and the chemicals we are exposed to I am worried about the future,' he told Daily Mail Online.

'I think the data serves as a wake up call, because I am personally worried about that [human extinction] if we do not address current environmental issues.'

Men in Western countries are becoming less fertile every year according to a new study (stock image)

Researchers at Hebrew University-Hadassah Braun School of Public Health and Community Medicine and the Icahn School of Medicine at Mount Sinai looked at 185 studies collected between 1973 and 2011 regarding sperm count and concentration in men from North America, Europe, Australia and New Zealand.

They found 59.3 percent average decline in total sperm count and a 52.4 percent average decline in sperm concentration among these men.

The men researched in those studies were not chosen for the studies based on their fertility status.

In contrast, there was no significant decline in South America, Asia and Africa, though far fewer studies have been conducted in those areas.

The research team then restricted the studies with a sample collection between 1996 and 2011, and found the slope to be equally steep and significant, indicating that the rate of decline is not decreasing.

This study did not examine causes of the decline, but it has previously been linked to environmental and lifestyle factors, such as exposure to chemicals and increased rates of obesity in Western countries.

'Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count, with the goal of prevention,' said Dr Levine.

Dr Levine also said the findings have public health implications because it demonstrates the proportion of men who are infertile are increasing.

Additionally, recent studies have found that reduced sperm count is related to increased morbidity and mortality, meaning the ongoing decline points to serious risks to male fertility and male health.

Sperm concentration: Researchers looked at 7,500 studies collected over the 37-year span and found that there was a 52.4 percent decline in sperm concentration

Sperm count: They also found a 59.3 percent decline in total sperm count in the men who were studied. Those men were not chosen based on fertility status

Decline in sperm rate has previously been linked to environmental and lifestyle influences such as prenatal chemical exposure, adult pesticide exposure, smoking, stress and obesity.

'Decreasing sperm count has been of great concern since it was first reported twenty-five years ago. This definitive study shows, for the first time, that this decline is strong and continuing,' explained Dr Shanna H Swan from Mount Sinai Hospital in New York.

'The fact that the decline is seen in Western countries strongly suggests that chemicals in commerce are playing a causal role in this trend.'

The decline in sperm counts among Western men has been reported since 1992, but previous studies have been considered controversial due to limitations.

In order to avoid those criticisms, in this study, researchers used a broader scope and rigorous meta-regression methods to conservatively address the reliability of study estimates.

They also controlled for factors that might explain the decline, such as age, abstinence time and selection of study population.