Newly released figures show a worrying decline in sperm count among men from Western countries, dropping 60 percent in 40 years.

In the first large-scale review of male sperm count, scientists have found a significant decline in sperm concentration and total sperm count among men from Western countries. Declines in sperm count have been reported since 1992, and the new statistics show no sign of that trend abating among Western men. The researchers found a 52.4 percent decline in sperm concentration, and a 59.3 percent decline in total sperm count,between 1973 and 2011 among men from North America, Europe, Australia and New Zealand. However, there was better news for men in South America, Asia and Africa, who showed no significant decline. Dr Hagai Levine, who led the research, says the results are a major wake-up call:

"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."

Dr Hagai Levine says that the proportion of men with sperm counts below the threshold for sub-fertility or infertility is increasing. Even more worryingly, given the findings from recent studies that reduced sperm count is related to increased morbidity and mortality, the ongoing decline points to serious risks to male fertility and health. Dr Shanna Swan, a professor at the Mount Sinai school of medicine in New York, says that 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. The fact that the decline is seen in Western countries strongly suggests that chemicals in commerce are playing a causal role in this trend."

While the research project did not look at causes of the observed declines, low and poor sperm count has previously been associated with environmental and lifestyle influences, including prenatal chemical exposure, adult pesticide exposure, smoking, stress and obesity. Levine and Swan say that declining sperm counts may reflect the impact of the modern environment and serve as a "canary in the coal mine" signalling broader risks to men's health.