Scientists warn of sperm count crisis : “serious public health warning”

Biggest-ever study confirms drastic decline in male reproductive health

Jeremy Laurance

Wednesday, 5 December 2012

The reproductive health of the average male is in sharp decline, the world’s largest study of the quality and concentration of sperm has found.

Between 1989 and 2005, average sperm counts fell by a third in the study of 26,000 men, increasing their risk of infertility. The amount of healthy sperm was also reduced, by a similar proportion.

The findings confirm research over the past 20 years that has shown sperm counts declining in many countries across the world. Reasons ranging from tight underwear to toxins in the environment have been advanced to explain the fall, but still no definitive cause has been found.

The decline occurred progressively throughout the 17-year period, suggesting that it could be continuing.

The latest research was conducted in France but British experts say it has global implications. The scientists said the results constituted a “serious public health warning” and that the link with the environment “particularly needs to be determined”.

The worldwide fall in sperm counts has been accompanied by a rise in testicular cancer – rates have doubled in the last 30 years – and in other male sexual disorders such as undescended testes, which are indicative of a “worrying pattern”, scientists say.

There is an urgent need to establish the causes so measures can be taken to prevent further damage, they add.

Richard Sharpe, professor of reproductive health at the University of Edinburgh and an international expert on toxins in the environment, said the study was “hugely impressive” and answered sceptics who doubted whether the global decline was real.

“Now, there can be little doubt that it is real, so it is a time for action. Something in our modern lifestyle, diet or environment is causing this and it is getting progressively worse. We still do not know which are the most important factors but the most likely are … a high-fat diet and environmental chemical exposures.”

Researchers from the Institut de Veille Sanitaire, St Maurice, used data from 126 fertility clinics in France which had collected semen samples from the male partners of women with blocked or missing fallopian tubes. The men, whose average age was 35, did not have fertility problems of their own and were therefore considered representative of the general male population.

The results, reported in the journal Human Reproduction, showed the concentration of sperm per millilitre of semen declined progressively by 1.9 per cent a year throughout the 17 years – from 73.6 million sperm per millilitre in 1989 to 49.9 million/ml in 2005. The proportion of normally formed sperm also decreased by 33.4 per cent over the same period.

Although the average sperm count of the men was well above the threshold definition of male infertility – which is 15 million/ml – it was below the World Health Organisation threshold of 55 million/ml which is thought to lengthen the time to conceive. Other European studies have shown that one in five young men has a sperm count low enough to cause problems conceiving.

Combined with other social trends, such as delayed childbearing which reduces female fertility, the decline in sperm counts could signal a crisis for couples hoping for a family.

Sperm count: How to boost it

1. Wear loose underwear – to make healthy sperm the testicles need to be below body temperature.

2. Eat food low in saturated fat.

3. Avoid smoking, drinking, using drugs and becoming obese.

4. Reduce exposure to industrial chemicals such as those used in making plastics – they can mimic the female hormone oestrogen countering male hormones.

5. Protect women in pregnancy – there is growing evidence that falling sperm counts may stem from effects in the womb.

6. Avoid anti-depressants – in rare cases they can cut sperm counts.

 

http://www.independent.co.uk/news/science/scientists-warn-of-sperm-count-crisis-8382449.html?printService=print

Ovaries continue to produce eggs during adulthood? Yes, they may….

A compelling new genetic study tracing the origins of immature egg cells, or ‘oocytes’, from the embryonic period throughout adulthood adds new information to a growing controversy

A compelling new genetic study tracing the origins of immature egg cells, or ‘oocytes‘, from the embryonic period throughout adulthood adds new information to a growing controversy. The notion of a “biological clock” in women arises from the fact that oocytes progressively decline in number as females get older, along with a decades-old dogmatic view that oocytes cannot be renewed in mammals after birth. After careful assessment of data from a recent study published in PLoS Genetics, scientists from Massachusetts General Hospital and the University of Edinburgh argue that the findings support formation of new eggs during adult life; a topic that has been historically controversial and has sparked considerable debate in recent years.

Eggs are formed from progenitor germ cells that exit the mitotic cycle, thereby ending their ability to proliferate through cell division, and subsequently enter meiosis, a process unique to the formation of eggs and sperm which removes one half of the genetic material from each type of cell prior to fertilization.

While traditional thinking has held that female mammals are born with all of the eggs they will ever have, newer research has demonstrated that adult mouse and human ovaries contain a rare population of progenitor germ cells called oogonial stem cells capable of dividing and generating new oocytes. Using a powerful new genetic tool that traces the number of divisions a cell has undergone with age (its ‘depth’) Shapiro and colleagues counted the number of times progenitor germ cells divided before becoming oocytes; their study was published in PLoS Genetics in February this year.

If traditional thinking held true, all divisions would have occurred prior to birth, and thus all oocytes would exhibit the same depth regardless of age. However, the opposite was found – eggs showed a progressive increase in depth as the female mice grew older.

In their assessment of the work by Shapiro and colleagues – published recently in a PLoS Genetics Perspective article – reproductive biologists Dori Woods, Evelyn Telfer and Jonathan Tilly conclude that the most plausible explanation for these findings is that progenitor germ cells in ovaries continue to divide throughout reproductive life, resulting in production of new oocytes with greater depth as animals age.

Although these investigations were performed in mice, there is emerging evidence that oogonial stem cells are also present in the ovaries of reproductive-age women, and these cells possess the capacity, like their mouse counterparts, to generate new oocytes under certain experimental conditions. While more work is needed to settle the debate over the significance of oocyte renewal in adult mammals, Woods and colleagues emphasize that “the recent work of Shapiro and colleagues is one of the first reports to offer experimental data consistent with a role for postnatal oocyte renewal in contributing to the reserve of ovarian follicles available for use in adult females as they age.”