Shorter spacing between births may raise risk of autism

Health Scan: Health Ministry works to make animal testing more humane; amniocentesis could be replaced by blood tests.

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January 23, 2011 02:11
Shorter spacing between births may raise risk of autism

medicines 88. (photo credit: )

 
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People who tend to raise large families won’t be pleased to hear about the latest retrospective study published in the journal Pediatrics, which found that the shorter the spacing between births, the higher the risk that the next child will suffer from autism. The research by Columbia University Prof. Peter Bearman and colleagues, who studied the records of over 500,000 California births between 1992 and 2002, suggests that babies born less than 24 months after their older sibling are significantly more likely to be autistic than those born at least three years afterwards.

The New York researchers controlled for the age of the parents and other factors and excluded children whose older sibling was autistic. They were surprised to find the connection, but found no other explanation than birth spacing, as they had ruled out subjects with other risks for autism. But the researchers stressed that more studies are needed to confirm their findings.

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Although the results were clear, the reasons for the phenomenon were not. It was suggested that the baby born within two years of a sibling’s birth might have suffered from inadequate nutrition, including lack of the B-vitamin folic acid, which can cause birth defects. It could also be a combination of factors.

Asked to comment, longtime Shaare Zedek Medical Center neonatologist Prof.

Arthur Eidelman told The Jerusalem Post that the finding was a “most intriguing observation, and compatible with previous observations that birth spacing is a factor in the health of the subsequent pregnancy; as shortened spacing is also associated with an increased rate of prematurity. As we do not fully understand the mechanism, I cannot say a nutrition supplement will solve the whole [autism] problem, but preconception supplementation of folic acid is definitely recommended.”

In 1998, British doctor Andrew Wakefield published a paper in The Lancet in which he claimed that autism was caused by measles-mumps-and rubella vaccination. Many people believed his findings and avoided giving their children MMR vaccines, thus leading to more cases. Almost a year ago, the journal apologized and retracted Wakefield’s paper when it was proven that his work was deliberately faked “junk science.” This was followed less than two weeks ago by an analysis in the BMJ (British Medical Journal) proving Wakefield’s study was fraudulent based on data falsification. According to experts, one out of 100 children suffer from some kind of autism, with it more common in boys than in girls.

STRICTER RULES FOR ANIMAL EXPERIMENTATION

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As two years have passed since the global Helsinki Declaration amendment protecting animals used in medical experimentation was not turned into an updated Israeli law, Health Ministry director-general Dr. Ronni Gamzu decided to introduce changes through a circular.

The previous rules going back to 1975 required all human medical experimentation to be preceded by experiments on animals. In 2000, the Helsinki Declaration added that animal experimentation may be carried out only “as appropriate,” meaning that only the minimum number of animals be included to reach conclusions regarding medications or procedures for human experimentation. In 2008, it was further updated to say that consideration must be taken to protect the animals’ welfare, meaning – among other things – that they should not suffer unnecessarily.

As nothing was done to make the 2008 amendment law in Israel, Gamzu said he would make it an “addition” to the previous law and release the stipulations to all relevant parties. Now, in every case of animal experimentation, only the number of animals needed to test efficacy and safety can be used, and the animals’ welfare must be protected. Gamzu continued that in each case, if simulations can be used instead of animal testing, animals should not be experimented on.

AMNIOCENTESIS COULD BE REPLACED BY BLOOD TEST

Hong Kong researchers have found that an experimental DNA blood test for pregnant women can almost eliminate the need for invasive amniocentesis or a chorionic villus sample to detect Down Syndrome in their fetuses. The need for invasive testing can be cut by 98 percent, according to Prof. Dennis Lo and colleagues from the Chinese University of Hong Kong, writing in the British Medical Journal (BMJ).

The blood test uses the latest DNA technology to analyze genetic components in the mother’s blood that indicate whether the fetus has the syndrome.

Down syndrome, caused by an extra copy of the 21st chromosome, occurs in around 1 in 800 births, but older women are at higher risk. Women in high-risk groups tend to undergo a combination of scans and hormone-level tests to determine if they need an invasive test, which involves taking samples of genetic material from the fetus. However, the tests carry a 1% risk of miscarriage.

The team used the most up-to-date DNA technology to test the blood samples from 753 pregnant women – all were at high risk of having a baby with Down’s – living in Hong Kong, the UK and the Netherlands. Eighty-six of the women were found to be carrying a fetus with Down syndrome. The results show that the test is highly accurate in detecting the syndrome, and does not give false negative results.

The authors concluded that the blood test could be used to accurately rule out Down syndrome among high-risk pregnancies before invasive sampling is considered, thereby reducing the number of invasive procedures.

NORMAL BODY TEMPERATURE HELPS FIGHT FUNGUS

Human body temperature – 37 degrees Celsius – is the perfect temperature to ward off fungal infection, but not so hot that we need to eat nonstop to maintain our metabolism, according to two researchers at Yeshiva University’s Albert Einstein College of Medicine in New York.

“One of the mysteries about humans and other advanced mammals has been why they are so hot compared with other animals,” said study co-author Prof. Arturo Casadevall, a microbiologist and immunologist at Einstein. “This study helps explain why mammalian temperatures are all around 37° C.”

The research builds upon his earlier work showing that the number of fungal species that can thrive and therefore infect an animal declines by 6% for every one degree Celsius rise in temperature. This means that tens of thousands of fungal species infect reptiles, amphibians and other cold-blooded animals, but only a few hundred harm mammals. Such protection against fungal infection, Casadevall has speculated, could have been crucial for the triumph of mammals following the age of dinosaurs.

Casadevall and his Einstein coauthor, Prof. Aviv Bergman, devised a mathematical model that analyzed the benefits gained by body temperatures that protect against fungi versus the costs (in terms of extra food consumption) required to maintain body temperatures between 30° and 40° C. The optimal temperature for maximizing benefits while minimizing costs was found to be 36.7° C, which is very close to normal body temperature.

“This study is a good example of how mammalian evolution has been driven by both external biological factors and internal physiological constraints,” Bergman concluded.

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