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发帖数: 2555 | 1 Sperm counts of men in North America, Europe, Australia and New Zealand are
plunging, according to a new analysis published Tuesday.
Among these men there has been a 52% decline in sperm concentration and a 59
% decline in total sperm count over a nearly 40-year period ending in 2011,
the analysis, published in the journal Human Reproduction Update, said.
Researchers led by Dr. Hagai Levine of Hebrew University of Jerusalem
examined thousands of studies and then conducted a meta-analysis of 185
studies. These included 42,935 male participants who provided semen samples
between 1973 and 2011. The chosen studies were well distributed over the
nearly 40 years of the study period and among 50 different countries. The
analysis included information on fertility status, age, ejaculation
abstinence time, semen collection method, sperm count method and geographic
location at the level of continent.
Based on their analysis, the international team of researchers from Brazil,
Denmark, Israel, Spain and the United States reported a decline in sperm
concentration of 1.4% per year with an overall drop of 52.4% during the
entire study period for men living in industrialized, Western countries.
Meanwhile, total sperm count among the same group plunged 1.6% per year and
59.3% overall. By comparison, the researchers found no significant declines
in the sperm counts and sperm concentrations of men living in South America,
Asia and Africa.
Michael Dourson, a professor in the Risk Science Center at the University of
Cincinnati College of Medicine, said in an email that "the overall work
appears to be solid with numerous safeguards for assuring systematic review
and data analysis." Dourson, who was not involved in the research, added, "
the observed trends appear to be real, and not based on chance findings."
Yet, Dourson noted that he wondered about the "functional significance of
the findings." The authors wrote that "poor sperm count is associated with
overall morbidity and mortality," yet Dourson noted that "longevity is
increasing" in Western countries so "these two observations do not appear to
match."
"I suspect that obesity may have something to do with these trends, but
measures of obesity, such as BMI (body mass-index) were not analyzed," said
Dourson, who was recently nominated to head the US Environmental Protection
Agency's Office of Chemical Safety and Pollution Prevention. "Overall,
however, a request for funding for further exploration seems well founded."
Dr. Harry Fisch, a clinical professor of urology at Weill Cornell Medicine,
said the results of this study are likely to be "real." Fisch, who has also
researched this topic -- though he was not involved in the current analysis
-- noted that one issue with all studies is the fact that sperm counting
methodologies have not been standardized across the globe or even within
most countries.
Another very important consideration is how geography influences sperm count
. "Even within the US, different states have different counts," said Fisch,
though all states fall within the range of normal. Fisch observed that the
new analysis did not delve into differences among countries.
The only environmental factor that's "not controversial" and "known to
influence sperm counts is temperature change," said Fisch, who noted that
sperm counts are known to vary by season and by climate. "I think global
warming, not phthalates, is responsible" for the declining rates seen here,
he said. Phthalates, found in everything from flooring to personal care
products, are one type of endocrine disrupting chemical.
"The impact of the modern environment on health of populations and
individuals is clearly huge, but remains largely unknown," said Levine. "
Sperm count has previously been plausibly associated with environmental and
lifestyle influences, including prenatal chemical exposure, adult pesticide
exposure, smoking, stress and obesity. Every man can reduce exposure to
chemicals, avoid smoking, keep balanced diet and weight and reduce stress." | r*s
发帖数: 2555 | | f****p
发帖数: 18483 | 3 撸多了的，肯定下降！
: 南美，亚洲，非洲没有下降
【在 r*s 的大作中提到】
: 南美，亚洲，非洲没有下降
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