Sperm concentration of men in Western countries has dropped by more than 50 percent in less than 40 years and there is no evidence that the decline is leveling off, a team of international researchers warned, based on a new and comprehensive study.
“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. Hagai Levine.
Levine, head of the Environmental Health Track at the Hebrew University-Hadassah Braun School of Public Health and Community Medicine in Jerusalem, led the study along with Dr. Shanna H. Swan, professor in New York’s Icahn School’s Department of Environmental Medicine and Public Health, assisted by researchers from Brazil, Denmark, Israel, Spain and the United States.
The findings have important public health implications.
Sperm count is the best measure for male fertility, and the data shows that the proportion of the male population with sperm counts below the threshold for subfertility or infertility is increasing.
In addition, recent studies have shown that reduced sperm count is also related to increased diseases and mortality among men, so the the ongoing “alarming” decline points to serious risks to male fertility and health, the researchers said.
The study also indicates that the rate of decline among Western men is not decreasing; in fact, the rate of increase was “steep and significant,” even when analysis was limited to those samples collected between 1996 and 2011.
Concentration of sperm and sperm count are two parameters used to determine the quality of sperm in men.
“This is a sign, like a canary in a coal mine,” Levine said in a phone interview .
“Besides the negative impact of declining sperm counts on fertility, the drop is also an alarm signal regarding the general health of humans.”
The study found a significant decline in sperm concentration and total sperm count among men from Western countries in the years between 1973 and 2011, in what the researchers say is the first systematic review and meta-analysis of trends in sperm count — a sort of a study of studies.
The paper was published Tuesday in Human Reproduction Update, a journal in the fields of reproductive biology, obstetrics and gynecology.
By screening 7,500 studies and conducting a meta-regression analysis on 185 of them between 1973 and 2011, the researchers found a 52.4% decline in sperm concentration, and a 59.3% decline in total sperm count, among men from North America, Europe, Australia and New Zealand who were not selected based on their fertility status.