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The international study, published in the journal Human Reproduction Update, which collaborates with the University of Murcia, establishes a rigorous analysis of trends of the last forty years showing that sperm concentration has decreased by more than 50% in Western men.
The research, conducted with studies between 1973 and 2011, also shows no signs of stabilizing in recent years.
These results suggest a significant decline in male reproductive health that has serious implications beyond fertility and reproduction, given the evidence linking poor seminal quality with an increased risk of hospitalization and death.
This project, led by the Hadassah Braun School of Public Health and Community Medicine at the Hebrew University and the Mount Sinai Icahn School of Medicine, reports a significant 52.4% decrease in sperm concentration, and a decrease of 59, 3% in the total count among men from North America, Europe, Australia and New Zealand who were not selected because of their fertility status.
However, this reduction was not observed in South America, Asia and Africa, where the number of studies has been lower.
All this has been done by screening 7,500 studies and conducting a meta-regression analysis in 185 studies.
It also indicates that the rate of decline is not decreasing among Western men: the slope is very steep and significant, even though the analyzes are restricted to studies that collected samples between 1996 and 2011.
Among the international teams collaborate the group Public Health and Epidemiology of the University of Murcia, whose principal investigator is Professor Alberto Torres, and Professor Jaime Mendiola.
The project was led by Dr. Hagai Levine, Head of the Environmental Health Area, Hadassa Braun School of Public Health and Community Medicine, Hebrew University of Jerusalem, with Shanna H Swan, Professor, Department of Environmental Health and Health Icahn School of Medicine at Mount Sinai in New York, along with researchers from Brazil, Denmark, Israel, Spain and the United States.
"The decline in sperm concentration has been known since 1992, but the issue remains controversial because of the limitations of previous studies. However, this new study has a broader scope and uses rigorous meta-regression methods, which allows Adequately address the reliability of the study estimates, and may also take into account other factors that could explain such decline, such as age, withdrawal time, and study population selection, "explains Mendiola.
This conclusive study shows, for the first time, that this decline is strong and continuous.
The fact that this decline is evident in Western countries suggests that marketed chemicals have a causal role in this trend.
"Given the importance of sperm concentration for male fertility and human health, this study is a wake-up call for researchers and health authorities around the world to investigate the causes of this steep decline, with a view to Prevention, "explains Hagai Levine, lead author and head of the Environmental Health Area at the Hadassa Braun School of Public Health and Community Medicine at the Hebrew University of Jerusalem School of Medicine.
"These findings have important implications for public health. First, they show that the proportion of men with a sperm count below the threshold of subfertility or infertility is increasing," says UMU professor Torres.
In addition, given the results of recent studies showing the relationship between reduced sperm concentration and increased morbidity and mortality, this continued decline indicates serious health and male fertility risks.
Although this research does not assess the causes of the observed decrease.
According to previous studies, this count is probably associated with environmental influences and lifestyles, including prenatal exposure to chemicals, and adults' exposure to pesticides, smoking, stress, and obesity.
Thus, it could accurately reflect the impact of the modern environment on male health throughout life.
Source: Universidad de Murcia
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