NEWSWEEK – Mothers exposed to higher traces of a common plastic chemical are more likely to give birth to sons with autism, a new study says.
Research found that developing boys exposed to traces of Bisphenol A (BPA) in the womb were six times more likely to receive a full diagnosis by the age of 11. They were also more likely to display autistic symptoms from as young as age 2.
Seventy pairs of new moms were monitored by experts at The Florey, Melbourne, Australia, one of the world’s best-known brain development facilities. Overall, the assessment period lasted a decade.
“Exposure to plastic chemicals during pregnancy has already been shown in some studies to be associated with subsequent autism in offspring,” Anne-Louise Ponsonby, professor and lead researcher, said in a statement. She feels this work will contribute to a better understanding of “part of the autism puzzle.”
BPA is used to harden plastics in household items such as food containers, glasses and water bottles. Broken down into microplastics, these substances work their way into the human body via the inadvertent absorption of plastic products.
Crucially, BPA works against healthy development in the womb through switching off the mother’s aromatase, an enzyme particularly important to the development of male fetuses.
Restricted maternal aromatase inhibitors are known to have profound implications on gestational development.
Why doesn’t the same thing affect young girls? An absence of healthy amounts of the enzyme is known to affect females later on, and physically, rather than neurologically, through the delayed development of secondary sex characteristics and balding.
The team fears that the ubiquity of plastic products means avoiding BPA is a near-impossible task …
Do vaccines cause autism?
“The Wakefield paper was found to be based on scientific misconduct.”
CHILDREN’S HOSPITAL OF PHILADELPHIA – Two studies have been cited by those claiming that the MMR vaccine causes autism. Both studies are critically flawed.
First study
In 1998, Andrew Wakefield and colleagues published a paper in the journal Lancet. Wakefield’s hypothesis was that the measles, mumps and rubella (MMR) vaccine caused a series of events that include intestinal inflammation, entrance into the bloodstream of proteins harmful to the brain, and consequent development of autism.
In support of his hypothesis, Dr. Wakefield described 12 children with developmental delay — eight had autism. All of these children had intestinal complaints and developed autism within one month of receiving MMR.
The Wakefield paper published in 1998 was flawed for two reasons:
- About 90% of children in England received MMR at the time this paper was written. Because MMR is administered at a time when many children are diagnosed with autism, it would be expected that most children with autism would have received an MMR vaccine, and that many would have received the vaccine recently. The observation that some children with autism recently received MMR is, therefore, expected. However, determination of whether MMR causes autism is best made by studying the incidence of autism in both vaccinated and unvaccinated children. This wasn’t done.
- Although the authors claim that autism is a consequence of intestinal inflammation, intestinal symptoms were observed after, not before, symptoms of autism in all eight cases.
This study was subsequently retracted; in scientific terms, this means that the paper is not part of the scientific record because it was found to be based on scientific misconduct. In this case, the studies were deemed fraudulent and data misrepresented.
Second study
In 2002, Wakefield and coworkers published a second paper examining the relationship between measles virus and autism. The authors tested intestinal biopsy samples for the presence of measles virus from children with and without autism. Seventy-five of 91 children with autism were found to have measles virus in intestinal biopsy tissue as compared with only 5 of 70 patients who didn’t have autism. On its surface, this was a concerning result. However, the second Wakefield paper was also critically flawed for the following reasons:
- Measles vaccine virus is live and attenuated. After inoculation, the vaccine virus probably replicates (or reproduces itself) about 15 to 20 times. Measles vaccine virus is likely to be taken up by specific cells responsible for virus uptake and presentation to the immune system (termed antigen-presenting cells or APCs). Because all APCs are mobile, and can travel throughout the body (including the intestine), it is plausible that a child immunized with MMR would have measles virus detected in intestinal tissues using a very sensitive assay. To determine if MMR is associated with autism, one must determine if the finding is specific for children with autism. Therefore, children with or without autism must be identical in two ways. First, children with or without autism must be matched for immunization status (i.e., receipt of the MMR vaccine). Second, children must be matched for the length of time between receipt of MMR vaccine and collection of biopsy specimens. Although this information was clearly available to the investigators and critical to their hypothesis, it was specifically omitted from the paper.
- Because natural measles virus is still circulating in England, it would have been important to determine whether the measles virus detected in these samples was natural measles virus or vaccine virus. Although methods are available to distinguish these two types of virus, the authors chose not to use them.
- The method used to detect measles virus in these studies was very sensitive. Laboratories that work with natural measles virus (such as the lab where these studies were performed) are at high risk of getting results that are incorrectly positive. No mention is made in the paper as to how this problem was avoided.
- As is true for all laboratory studies, the person who is performing the test should not know whether the sample is obtained from a case with autism or without autism (blinding). No statements were made in the methods section to assure that blinding occurred.
Studies showing that MMR vaccine does not cause autism
Several studies have been performed that disprove the notion that MMR causes autism.
Brent Taylor and co-workers
In 1999, Brent Taylor and co-workers examined the relationship between receipt of MMR and development of autism in an excellent, well-controlled study. Taylor examined the records of 498 children with autism or autism-like disorder.
Cases were identified by registers from the North Thames region of England before and after the MMR vaccine was introduced into the United Kingdom in 1988. Taylor then examined the incidence and age at diagnosis of autism in vaccinated and unvaccinated children. He found that:
- The percentage of children vaccinated was the same in children with autism as in other children in the North Thames region.
- No difference in the age of diagnosis of autism was found in vaccinated and unvaccinated children.
- The onset of symptoms of autism did not occur within two, four, or six months of receiving the MMR vaccine.
Madsen and colleagues
One of the best studies was performed by Madsen and colleagues in Denmark between 1991 and 1998 and reported in the New England Journal of Medicine. The study included 537,303 children representing 2,129,864 person-years of study. Approximately 82% of children had received the MMR vaccine.
The group of children was selected from the Danish Civil Registration System, vaccination status was obtained from the Danish National Board of Health, and children with autism were identified from the Danish Central Register. The risk of autism in the group of vaccinated children was the same as that in unvaccinated children. Furthermore, there was no association between the age at the time of vaccination, the time since vaccination, or the date of vaccination and the development of autism.
Subsequent studies and meta-analysis have corroborated the findings that the MMR vaccine does not cause autism.
Watch as Dr. Offit talks about vaccines and autism in this short video, part of the Talking about Vaccines with Dr. Paul Offit video series.