THERE is no evidence to support the widely held belief that we are in the
grip of an autism epidemic, says a leading researcher in Britain. What鈥檚 more,
there has been no increase in the proportion of children who have 鈥渞egressive
补耻迟颈蝉尘鈥�.
A few researchers believe the combined measles, mumps and rubella (MMR)
vaccine triggers autism. They point to an apparent rise in cases since the
introduction of MMR in the 1980s
(快猫短视频, 3 February, p 8).
Before the 1980s, only 1 in 2500 children were diagnosed as autistic. Recent
studies put the figure as high as 1 in 250.
But Eric Fombonne, a psychiatrist at Maudsley Hospital in London, says that
none of these studies shows a real rise in autism. 鈥淭hat rates in recent surveys
are substantially higher than 30 years ago merely reflects the adoption of a
much broader concept of autism, a recognition of autism among normally
intelligent subjects and improved identification of persons with autism,鈥� he
says.
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In a paper published in Pediatrics last week (vol 107, p 411),
Fombonne is particularly critical of a 1999 report from California widely quoted
as proof of a dramatic rise in autism. Fombonne says the study doesn鈥檛 allow for
the rise in California鈥檚 population in recent years. Nor does it take into
account changes in the definition of autism, or the fact that autistic children
are now diagnosed at a much earlier age.
In particular, Fombonne says, many people have misinterpreted a graph that
appears to show a sudden rise in cases of autism during the 1980s. The graph in
fact shows the number of people known to have autism in a single year, 1991,
plotted against their year of birth. The rise in cases for birth dates nearer
the present could reflect the rising population and improved diagnosis among
young children. Portraying the data in this way is very misleading, Fombonne
says. 鈥淭rying to link this with MMR is complete nonsense.鈥�
A study that will be published in the British Medical Journal this
week backs up this view. Researchers at Boston University School of Medicine
failed to find any connection between the rise in the number of cases reported
by doctors and the introduction of MMR in 1988.
In an unpublished study, Fombonne has also looked to see if the number of
children with regressive autism has changed. Children with this kind of autism
seem to develop normally, only to regress and lose some skills they have
learned. MMR and other environmental factors have been blamed for these
cases.
But when Fombonne compared a Maudsley Hospital study of autistic children
born before 1980 with a study of autistic children in Stafford born between 1992
and 1995, he found no change in the proportion of children with regressive
autism. 鈥淭he rates of regression in both samples are strikingly similar,鈥� he
says. 鈥淎bout one [autistic] child in six has some degree of regression.鈥�
Fombonne鈥檚 analysis of the data is reasonable, says David Potter of Britain鈥檚
National Autistic Society, but he hasn鈥檛 proved that the increase in autism is
solely due to changes in diagnosis. 鈥淭here are no baseline figures to compare
with,鈥� Potter says. 鈥淢aybe there is an environmental factor鈥攂ut we don鈥檛
know what it is.鈥�