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MMR/autism link is unlikelyBupa investigative news - 28 July 2003
According to new research, cases of the developmental disability autism, which was controversially associated with the triple MMR immunisation, have levelled out since 1992. The new research suggests that the rise in cases since 1979 may not have been "real", but rather the result of better awareness, diagnosis and record keeping. They also suggest that some parental claims of a link between MMR and autism may have increased after the immunisation debate arose in 1997. But what data did the researchers look at and what do their findings really mean? What were the headlines?News of the research made the majority of newspapers in the UK, from tiny mentions to lengthy examinations. Reports gained headlines such as, "New study rejects MMR link to autism rise", "Questions over MMR autism link", "Autism surge 'never happened'", "Study casts doubt on autism link with MMR", and "'Proof' that MMR jab does not cause autism". What is the bigger picture?The paper was published in the journal Archives of Disease in Childhood and was carried out by Professor B. Taylor and colleagues from the Royal Free Hospital and University College Medical School in London. They followed up previous research they conducted, involving 567 children with autistic spectrum disorder in five districts of north east London. All the children were born between the years 1979 and 1998. Their previous study indicated that the numbers of new cases reported has increased yearly between 1979 and 1992, but data from the additional two and a half years of research included in this study show this rise has stopped. In fact, the figures show a levelling out of 45 to 50 cases a year between 1992 and 1996, which is equivalent to 2.6 cases per 1000 live births. They also noted that the age at which children were diagnosed with autism has been falling since 1985. According to the researchers, these could factors could be due to better recognition and diagnosis of autism. They write that it's possible, "that the earlier recorded rise in prevalence was not a real increase, but was likely due to factors such as increased recognition, a greater willingness to accept the diagnostic label, and better recording systems". The team also discovered that the triggers that parents believed were a cause of their child's autism differed before and after the MMR vaccine debate. The number of parents blaming the triple vaccine has risen since August 1997, when the original paper by Dr. Wakefield, linking the jab with bowel disease and autism, was published. Before August 1997 only two sets of parents out of 46 cited the MMR jab, after 1997 six out of 30 sets of parents claimed it was a trigger. "Parents are usually very reliable historians regarding their child's early life," the researchers wrote. "Sometimes, however, there is the possibility of recall bias, in some instances reflecting changing beliefs about causal relationships." Their paper concludes that these findings support the view that MMR is not linked to autism. "The claims that MMR vaccine is involved in the initiation of autism, and/or with regression, and/or with bowel problems associated with autism are not supported by any credible scientific evidence, while there is compelling and increasing evidence showing no association."
What does this mean?The National Autistic Society (NAS) is not able to comment directly on the autism/MMR issue, preferring instead to hold a neutral stance. However it welcomed the research. Stuart Notholt, director of policy and public affairs explained that the finding that the yearly numbers of autism diagnoses levelled off is not surprising. The rise in diagnoses would be due to cases that would once have been missed being recognised due to increased awareness of the disease. Once almost all of the children who have autism are being routinely diagnosed, the yearly numbers of diagnoses should remain steady. The levels would then only rise if there was an external factor that was a work to cause more children to develop the disease. "It might be expected that with growing familiarity with autistic spectrum disorders, over a period of time, provided there were no external factors influencing onset, prevalence figures would begin to level out," he said. Dr. Annabel Bentley, Bupa assistant medical director, described the study as "important" and said, "Although there has been a huge media controversy over MMR, there isn't a scientific controversy. Actually, there are only one or two scientific papers that show that MMR might be linked to autism. The vast majority of all papers reporting it don't show a causal link between MMR and autism and, in fact, give evidence to disprove the link." Although interested in the study, Jackie Fletcher, from the campaign group JABS (Justice Awareness and Basic Support) feels "it's a missed opportunity". Explaining her views, she said that the researchers should have interviewed the parents of the children directly to get their views on what caused the autism. "The authors have elected to go over old data, which really doesn't give us any new information. They haven't done any actual clinical investigation of the children. Instead, it's been based on GP records, hospital notes and health visitor notes. Although we accept that medical records and GP notes are important, we think a vital element in any kind of research is to take personal testimonies from the families and look at what happened to the child shortly after the vaccine." Jackie, whose own son was hospitalised due to convulsions 10 days after receiving his MMR vaccine in 1992, remains unconvinced about the safety of the vaccine. "My own feeling is that parents have a right to be concerned," she said. "I'm not against vaccines, and I'm not trying to have a child seriously affected by measles, but I don't want them affected by a vaccine either. People know that some products don't suit some individuals, yet they're trying to claim every child is identical and will react in the same way to the MMR vaccine."
What does this mean to me?According to Stuart Notholt, this isn't the first time rise in autism has been attributed to a better awareness of the condition. "The rise in reported cases in autism have been reported in other papers, and attributed to autistic spectrum disorders being more widely recognised and changes in diagnostic criteria, but whether there has been a true increase in the incidence of autism is not known," he said. Deciding whether to have the vaccine can be tricky, but it's important to weigh up the health benefits and risks. "We can empathise with parents that it's a difficult decision to make," said Dr. Annabel Bentley. "The MMR debate has created a lot of uncertainty, confusion and worry about what is the best thing to do. My advice would be to discuss it further with your GP, practice nurse or health visitor and get more information. It's not for any organisation to tell parents what to do, but they need to get the full facts and all the information in order to make a decision." Some of the important things to bear in mind, said Dr. Bentley, is that autism has been around for a long time - it was first identified by Kanner in 1943 - and there have been many cases since then. The triple MMR vaccine wasn't introduced until 1988, yet before that point, there were many cases of autism. "Previous epidemiology studies have looked at the figures and found that when MMR was introduced in 1988 there was no sudden jump in numbers of cases of autism. But, if MMR did cause autism, you would expect to see a sudden rise in cases when it was started and this isn't the case," she explained. For parents worried about autism, Dr. Bentley recommends contacting the National Autistic Society (NAS) for more information. If you're worried your child could have autism, specific behaviours that should be discussed with a GP include:
SummaryThis scientific research adds to the findings from other studies suggesting autism isn't linked to the MMR vaccination. For families and those affected by autism, it's encouraging that diagnoses are being made earlier and that the condition has gained extra recognition over the years. Links for more information
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