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Is the United States in a baby crisis? Some demographers are freaking out, as the number of women giving birth has declined for years and just hit a historic low. If the trend continues — and experts disagree on whether it will — the country could face economic and cultural turmoil. FULL STORY
Sperm Count Drops 50 Percent In U.S. & Other Parts Of The World
The quality of sperm from men in North America, Europe and Australia has declined dramatically over the past 40 years, with a 52.4 percent drop in sperm concentration, according to a study published Tuesday.
The research - the largest and most comprehensive look at the topic, involving data from 185 studies and 42,000 men around the world between 1973 and 2011 - appears to confirm fears that male reproductive health may be declining.
The most important data points in the new study involved sperm concentrations for what are known as "unselected" men who haven't yet proven they are fertile. These are men in the studies who are on the younger side and are not yet fathers or do not have partners who are pregnant. Researchers estimated that these men had an average sperm concentration of 99 million per milliliter in 1973 but that that had dropped to an average 47 million per milliliter in 2011.
That is a disturbing number given that, according to World Health Organization criteria, men with a sperm concentration of less than 40 million are considered to have an impaired chance of conceiving and those with a sperm concentration of less than 15 million per milliliter are unlikely to be able to have children.
These numbers mean "surprisingly higher proportions of men are falling into the infertile and sub fertile categories," said Shanna H. Swan, one of the authors of the new study published in the Human Reproduction Update.
There are numerous theories about what may be happening to sperm. Many scientists say the most sensitive period may be during the first trimester, when the developing fetus's reproductive system may be impacted by a mother smoking, stress she experienced or food she ate. Exposure to chemicals that can change hormone levels, known as endocrine disrupters, are among the issues being studied.
Over the life span, men are also exposed to a number of other things that could potentially influence sperm concentration: pesticides, lead, X-rays, stress and countless other factors.
The changes in the womb can cause permanent damage, Swan explained, while the adult exposures are mostly reversible.
The issue of sperm isn't just about having babies. It has larger implications for men's health. Poor sperm health has been linked to cardiovascular issues, obesity, cancer and more generally to higher rates of hospitalization and death. While men's life expectancy is increasing overall thanks to advances in medical care, nutrition and sanitation, it isn't unthinkable that that could one day reverse.
"Having a low sperm count is a signal," Swan said, "that there's something wrong in men's health overall."
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