A new study found that the quality of sperm from men in North America, Europe, and Australia has declined considerably over the past 40 years. The researchers of the new research —published Tuesday in the journal Human Reproduction Update— said that over that period there has been a 52.4 percent decrease in sperm concentration among men from Western countries.
The study looked at data from 185 studies and 42,000 men worldwide between 1973 and 2011.
Previous studies had already shown the quality of sperm in men has been declining considerably in recent years, and the new study proves that hypothesis.
Western men have lower sperm concentration and count than they did in 1977
Researchers from the Icahn School of Medicine at Mount Sinai and the Hebrew University-Hadassah Braun School of Public Health and Community Medicine conducted the study, where they screened more than 7,500 studies and performed a meta-regression of analysis of 185 studies
They found a 52.4 percent decline in sperm concentration, as well as a 59.3 percent drop in total sperm count, among men from Europe, North America, Australia and New Zealand.
“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, lead author of the study from the Hebrew University of Jerusalem’s Faculty of Medicine, according to EurekAlert.
The authors noted the males in these studies were not selected based on their fertility status. Furthermore, the results for Western men were different from those among men in South America, Asia, and Africa, where the authors found no significant declines. However, it’s important to highlight that fewer studies focus in those regions compared to Western countries.
The researchers also noted that the rate of sperm count decline among Western men is not decreasing. Even between 1996 and 2011, when fewer studies were conducted, the drop was steep and significant, they said.
‘Results suggest chemicals in commerce are playing a causal role in this trend.’
Declines in sperm count have been reported since 1992, but most of those findings have been rejected or dismissed over factors like the age of the men included methodology approach, the size of the studies, and bias in counting systems.
However, the authors stressed the new study used a broader scope as well as rigorous meta-regression analyses. Thus, the team was able to correctly weigh in the data and controlled factors that might explain the sperm decline such as age, abstinence, and selection of the study population.
The researchers said their study has important public health implications, as their findings show that the proportion of Western men with sperm counts below the subfertility or infertility mark is increasing. Plus, the findings add to the recent research that suggests that reduced sperm count is related to increased morbidity and mortality. Should this sperm decline proceed, male fertility and health overall could be severely affected.
“Decreasing sperm count has been of great concern since it was first reported twenty-five years ago,” said Dr. Shanna Swan, a professor at the Icahn School of Medicine at Mount Sinai. “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.”
Poor sperm health is linked to numerous health adversities
The study mainly focused in sperm concentrations for “unselected” men, or men who haven’t yet proven they are fertile, referring to males in the studies who are young and haven’t fathered any child, or who don’t have partners who are pregnant.
The researchers estimated these “unselected” men had an average sperm concentration of 47 million per milliliter in 2011, compared to a concentration of 99 million per milliliter in 1973. The World Health Organization has said that men with a sperm concentration of less than 40 million per milliliter are considered to have an impaired chance of conceiving. Moreover, WHO says that men with a concentration of less than 15 million are unlikely to be able to conceive.
“Having a low sperm count is a signal, that there’s something wrong in men health overall,” Swan told The Washington Post.
The authors of the new study didn’t analyze the causes of the dramatic decline in sperm count. However, sperm count decline is linked to environmental and lifestyle influences, such as smoking, stress, obesity, prenatal chemical exposure, and adult pesticide exposure. Poor sperm health can result in cardiovascular disease, obesity, cancer, and higher rates of hospitalization and death.