viernes, 28 de julio de 2017

Every sperm is scarce… | MercatorNet | July 28, 2017 | MercatorNet |

Every sperm is scarce…
| MercatorNet | July 28, 2017 | MercatorNet |

Every sperm is scarce…

How can the west have more babies if sperm counts are in steep decline?
Marcus Roberts | Jul 27 2017 | comment 

Over the years there are have been studies that have raised concerns about the possibility of declining sperm count of men in the western world (North America, Europe, New Zealand and Australia). However, many of these studies have been criticised for not taking into account changing, more accurate laboratory methods, not being of a sufficient size and for not involving men without infertility problems or disease. According to the Guardian newspaper however, a new study has come to very similar conclusions as previous studies and has avoided many of the criticisms of them.
The study was undertaken by an international team of researchers and was published in the journal Human Reproduction Update. It drew upon 185 studies conducted between 1973 and 2011 which collectively involved 43,000 men throughout the western world. The study analysed only studies that used the same sperm count method, were of a reasonable size and involved men not known to have fertility problems or disease. After taking into account factors like age and the length of time since previous ejaculation, the study found that sperm concentration had fallen from 99 million per ml in 1973 to 47.1 million per ml in 2011. This was a decline of 52.4%. Furthermore, the total sperm count in a semen sample fell by just under 60%. According to Hagai Levine, an epidemiologist from the Hebrew University of Jerusalem and the lead author of the study “the results are quite shocking”. It certainly appears that way to an uninformed outsider! Levine continued:
“this is a classic under the radar huge public health problem that is really neglected.”
Turning to those in the field who were not involved in the study, the response has been varied. An expert in male reproductive health and professor at the University of Edinburgh, Richard Sharpe, (I assume he isn’t also the rifleman from the Peninsular War…) said that the study addressed many of the problems in previous studies and that it “is about as close as we are going to get” to being sure of the decline. But he also noted that reasons for the decline are unclear, primarily because male reproductive health research is not a high priority.
Others are less convinced by the study. Tina Kold Jensen of Syddansk University in Denmark said that the she was surprised by the findings. She had been involved in a study looking at young men recruited for military service over 15 years in Denmark which found no such decline. Professor of andrology at the University of Sheffield, Allan Pacey, said that the study was the best he’d read on the decline but that it was unclear if the trend was real. Instead he favoured an approach that tested a large number of young men every year in a single country over a long time frame (up to 25 years) which would be a better measure if there was such a decline. (I sense a grant application coming up…) On the other hand Pacey did agree there was cause for concern about male reproductive health, pointing to the increase in testicular cancer.
Furthermore, if the decline is real, there is little consensus about what is causing it. Increases in body weight, a lack of physical activity, smoking, exposure of pregnant women to endocrine disruptors in household cleaning products have all been touted as reasons for the decline.
What about demography? Well many of the countries in the western world have seen their fertility rates decline since 1973. Many are no sitting about below the population replacement threshold of 2.1 children per woman. Could sperm count be something to do with it? Perhaps. According to Pacey:
“If you are a guy with a low sperm count and you try for a baby when you are 21, you are probably not going to notice you’ve got a problem … But if you are trying with your partner when she is 35 then that’s when the heartache comes, because by then you have got low sperm count, you’ve got an older partner and you haven’t got a lot of time to try and fix it medically.”
In short, delaying having children too long may make it harder to have children. Delaying having children too long when you have low sperm count makes it even harder. In the west, we are having fewer babies. We also seem to have much less sperm.

July 28, 2017

Part of Facebook CEO Mark Zuckerberg's job description is being a visionary. So it was gratifying to read of his enthusiasm for Africa. "There's this energy here, you feel it as soon as you get off the place," he said in Lagos last year. "The world needs to see that.  Here is Lagos, and across the continent, things are really shifting. Things are moving from a resource-based economy and its shifting to entrepreneurial, knowledge-based economy. It's not only shaping the country but the whole continent." 
With Europe, North and South America and Australia's population declining, Africa is poised to be the future of the world. So that's why it's so disheartening to read hackneyed "population bomb" arguments retailed by the new French President. In today's lead article Mathew Otineo contends that "M. Macron’s proclamations were extremely crude, offensive, insensitive and paternalistic. And, coming from a 39-year-old man with no children, they were what an African with his wits around would also call disrespectful." Africa has many problems, but over-population is not one of them. 

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