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A 38-year long study has concluded sperm concentration among men living in North America, Europe, Australia, and New Zealand has declined by more than 50 percent between 1973 and 2011. Led by fertility academics from the Hebrew University of Jerusalem—and analysing data gathered by researchers from all over the world—the study was published on Tuesday in the peer-reviewed journal Human Reproduction Update.
The sperm concentration levels of 43,000 men were tested over the 38-year period, none of them selected based on their fertility status or concerns about sperm count. Researchers took into account thousands of fertility tests conducted over time in Western countries and found a 52.4 percent decline in sperm concentration, and a 59.3 percent decline in total sperm count. In contrast they noted "no significant decline" in sperm concentration or count in South American, Asian, or African men—but fewer longterm fertility studies have been conducted in those geographic areas.
Most troublingly, the research indicates the rate of sperm decline among Western men isn't slowing down—when analysis of the data was restricted between 1996 and 2011, sperm count and concentration declined continued at a severe level of around 1.4 percent each year. According to the study, "the proportion of men with sperm counts below the threshold for subfertility or infertility is increasing" and, given the relationship between reduced sperm count and mortality, "the ongoing decline points to serious risks to male fertility and health."
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In a media release, lead author of the study Dr Hagai Levine said the public health implications of the research were troubling. "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," he said.
This study did not suggest possible causes for the incredible decline, but previous research into this area has linked decreased sperm concentration to chemical exposure, pesticide exposure, smoking, stress, and obesity.
Dr Shanna H Swan, a professor in the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai, New York, highlighted the risks that the Western lifestyle poses toward sperm count and concentration.
"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," she said.
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