Sperm levels among Western men have plummeted to a record low, warns new research.
The study shows that the sperm count among men from Europe, North America and Australia has fallen by more than 50 per cent in 40 years.
And the study indicates the rate of decline is not slowing down - with sample collections between 1996 and 2011 still showing sharp decline.
Scientists have suggested that ‘chemicals in commerce’ are partly to blame for the stark numbers.
The study, published by researchers from the Hebrew University-Hadassah Braun School of Public Health and Community Medicine and the Icahn School of Medicine at Mount Sinai, screened 7,500 studies that took place between 1973 and 2011.
The researchers found a 52.4 per cent decline in sperm concentration, and a 59.3 per cent decline in total sperm count, among men from North America, Europe, Australia and New Zealand who were not selected based on their fertility status.
In contrast, no significant decline was seen in South America, Asia and Africa, where far fewer studies have been conducted.
The research, published in the Human Reproduction Update, was led by Dr. Hagai Levine with Dr. Shanna H Swan and an international team of researchers from Brazil, Denmark, Israel, Spain and the United States.
While declines in sperm count have been reported since 1992, the question has remained controversial because of limitations in past studies.
However, the current study uses a broader scope and rigorous methods, conservatively addresses the reliability of study estimates and controls for factors that might help explain the decline such as age, abstinence time, and selection of the study population.
Dr Levine said: “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 Swan added: “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 current study did not examine causes of the observed declines, sperm count has previously been plausibly associated with environmental and lifestyle influences, including prenatal chemical exposure, adult pesticide exposure, smoking, stress and obesity.
Therefore, sperm count may sensitively reflect the impact of the modern environment on male health across the lifespan and serve as a “canary in the coal mine” signalling broader risks to male health.