Wall Street Journal How Many Kids Have Autism? November 30, 2006

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THE NUMBERS GUY

By CARL BIALIK

How Many Kids Have Autism?

November 30, 2006

Several skeptical Numbers Guy readers have suggested I look into an

alarming claim: that one in 166 U.S. children has autism.

That stat has received a lot of attention recently in advocacy

materials, television ads and newspapers, including reports in the

Dallas Morning News, the Chicago Tribune and the Savannah Morning News.

How important is it to accurately count the number of children with

autism? Does the one-in-166 number seem too high, or too low, or

accurate? Do you generally believe statistics on the number of people

suffering from conditions? Do such numbers affect your opinions? Join a

discussion with Carl Bialik.

Autism experts told me that research broadly supports the estimate --

with two major caveats. Those caveats help explain why the stat, while

alarming, doesn't support related claims by some advocates: that autism

cases have been mushrooming with " epidemic speed, " and that more than

one million Americans have autism.

First, the stat comes from figures published by the Centers for Disease

Control and Prevention, based on a review of several studies that came

up with estimates. But the CDC was careful to point out that the

studies produced a wide range of results. Indeed, the headline-grabbing

number focuses on the worst-case scenario: The CDC said the number of

children with autism was somewhere between one in 500 and one in 166.

Second, the numbers take into account a relatively modern definition of

autism that includes a full range of disorders. The changing definition

of autism has played a major role in influencing statistics.

The cause of autism isn't completely understood; a combination of

genetic and environmental factors is believed to play a part, according

to the CDC. Autism can usually be diagnosed before the age of three,

according to the National Institute of Health. Different from mental

retardation, autistic disorders (as they are now defined) are

characterized by impairment in communication and other social

interaction. Mental retardation, characterized in part by a low

intelligence-test score, can coincide with autism, but some people with

autism have above-average IQs.

Those with " high-functioning autism " or with Asperger's Disorder --

distinguished by less-severe symptoms that may not become apparent

until later in life -- are likely to have an easier time of adapting to

mainstream society, and therefore their conditions can be more

difficult to diagnose. Other people with more severe cases of autism

may require special education throughout school years and may have

difficulty living independently as adults.

The broad definition used to arrive at the one-in-166 figure, which

includes milder forms like Asperger's syndrome, was published by the

American Psychiatric Association in 1994 in the Diagnostic and

Statistical Manual of Mental Disorders, Fourth Edition, known as the

DSM-IV -- the primary handbook for diagnosing mental disorders.

Fombonne, an autism expert at Montreal's McGill University, told

me that while about a dozen studies around the world have found autism

prevalence rates that would be in line with the one-in-166 estimate,

that same research found that the majority of those people had a mild

form of the condition.

The high profile of the one-in-166 number has been driven by increased

public-awareness campaigns about autism from the government and

advocacy groups. In 2004, the CDC, the Department of Health and Human

Services, the American Academy of Pediatrics and other groups issued an

alert (Autism A.L.A.R.M.) to doctors citing the 1-in-166 stat and

advising on how to screen for cases. Since then, the CDC has reaffirmed

the number in an online fact sheet (where it cited the broad range of

estimates) and in a May report in its Morbidity and Mortality Weekly

Report -- the latter was based on parents' self-reporting of their

doctors' diagnoses. Meanwhile, an even more recent U.K. study published

over the summer in the Lancet found a rate of children with autism of

between one in 110 and one in 70.

The CDC has increased research spending on autism by 80% since 2002, to

$15.1 million this year. (Autism groups say the government is still

spending too little on research and support for parents and adults with

autism.)

A nonprofit autism-advocacy group called Autism Speaks put the

one-in-166 stat front and center in a media campaign distributed by the

nonprofit Ad Council. The organization has grown quickly since

launching last year, and is distributing $15 million in research funds

this year, spokeswoman Arons told me. " We're using what is a very

well-known, well-accepted number, " she said. " We don't want to be

alarmists; we want to be accurate. "

The nonprofit Autism Society of America, one of the oldest and largest

autism groups, has seen its budget grow steadily in recent years, to

about $20 million this year, President Lee Grossman told me. He

attributed the increased donations to greater public awareness.

" The one in 166 has been the biggest boon to awareness we've had, " said

Marguerite Colston, director of communications for the Autism Society.

" Those kinds of numbers stop people in their tracks, as they should. "

More Numbers

Equally galvanizing but more questionable are claims by some advocates,

including the Autism Society, that autism prevalence has grown rapidly.

An Autism Society Web page said autism is " the fastest-growing

developmental disability, " and said the number of people with autism

increased 172% in the 1990s while population rose 13%.

Trend figures for autism are difficult to pin down. Most of the

scientific studies looking at the size of the autistic population have

been completed relatively recently, and don't have historical

comparisons, a point made in a 2001 paper by Dr. Fombonne questioning

the existence of an autism epidemic.

Some groups (including the Autism Society) publish trend figures based

on data collected from the Department of Education, which compiles

counts of students with various disabilities as part of the Individuals

with Disabilities Education Act. But changes in the way data are

classified and handled have made that database an unreliable source for

determining trends.

Until 1993, autism was lumped into other categories, such as mental

retardation or emotional disturbance. Even after schools were asked to

report autism separately, they labored initially under a narrower

definition that preceded the DSM-IV. It took schools years to report

more fully and catch more cases, a Posny, director of special

education programs at the Department of Education, told me. That made

comparisons with figures before 2000 difficult. " We're better at

diagnosing and catching the students much earlier " now, Ms. Posny said.

There has been a doubling since 2000 in the number of students aged six

to 21 that schools identified as having autism, to 166,000 in 2004 from

80,000 in 2000. (Again, these figures use a broad definition of

autism.) Several experts I spoke with told me they believed the

increase has more to do with better record keeping and diagnosis than

an increase in the number of autistic children.

Goodman, associate professor of oncology, pediatrics,

epidemiology and biostatistics at the s Hopkins Schools of Medicine

and Public Health, told me in an email, " There have been a number of

excellent papers that concluded that the definitions of autism are

wholly to blame for the alleged increase in incidence; others have

concluded they are partly to blame, and that some component of the

increase is real. What is almost certainly not true is that this rate

represents a 10- or 20- or whatever-fold increase in autism rates since

the 1980s, which many quite vocal activist folks have claimed and

vigorously promoted. "

Ms. Colston agreed that some of the growth the Autism Society cites can

be attributed to improved diagnostics and reporting. " Diagnostics have

improved so much, " she said. But she added that other evidence,

including reports from her group's members and from overtaxed state

agencies, suggests a very real increase in incidence. " That's what we

believe, and what we see, " Ms. Colston said.

The national media has also, at times, promoted the concept of an

autism epidemic. Responding to some of these claims, Morton Ann

Gernsbacher, professor of psychology at the University of Wisconsin,

co-authored a paper last year in Current Directions in Psychological

Science titled, " Three Reasons Not to Believe in an Autism Epidemic. "

One of her reasons stemmed from a close examination of data from

California used to show a 273% increase from 1987 to 1998. Prof.

Gernsbacher showed how broader diagnostic criteria " will result in a

dramatic increase in diagnosed cases. " For example, among a sample of

students diagnosed with autism before the broader DSM-IV definition was

published in 1994, 61% were identified as having intellectual

impairments. But only 27% of a more recent group of children

categorized as autistic had such impairments.

As for the Department of Education data, the paper pointed out that

other reporting categories showed huge growth immediately after they

were introduced, as schools got on firm footing with new definitions.

The number of students reported as having traumatic brain injuries

soared more than 50-fold in the decade after it was introduced as its

own category in 1991. Counts for children with " developmental delay, "

meanwhile, rose more than seven-fold in the three years after that

category was introduced in 1997.

Counting Everyone

The Autism Society also states that one to 1.5 million Americans have

autism, a number derived by applying the CDC range of prevalence among

children to an estimate of the general U.S. population of 300 million

(and then applying some major rounding). Other advocacy groups cite a

prevalence of 1.7 million, which based on the most recent decennial

census's estimate of 280 million Americans.

But the available studies are all based on children. " We really do not

have a sense of how many adults would have been diagnosed with

current-day criteria when those adults were children, " the University

of Wisconsin's Prof. Gernsbacher said.

Ms. Colston said of the Autism Society's estimate for total U.S.

population: " It's not a hard, fast, scientific number. " She added that

generally, there is a need for more study -- and funding -- for adult

autism. " It's the area of awareness that really needs to take off, and

that includes statistics, as there aren't enough statistics on it, " she

said.

The bottom line: Stripped of spin and taken in context, the one-in-166

estimate does appear to be sound, if overly simplified.

Marshalyn Yeargin-Allsopp, a medical epidemiologist with the CDC in

Atlanta, said autism studies can be particularly complex -- hence the

CDC's reported range. But she understands the desire to reduce the

research into a convenient number. " The general public, they want one

number. All this information, across studies, areas, populations, they

want to distill into one number, " she said. " My response is: It depends

upon the methods used. There's not just one number out there. "

* * *

Thanks to everyone who posted to the most recent forum about my column

on the accuracy of polls before this month's elections. I'll be

reading, and responding to, your comments about autism numbers in a new

forum this week. And please remember to use your full name with posts.

(If you have a comment or suggestion unrelated to this week's column,

please email me directly at numbersguy@....)

Write to Carl Bialik at numbersguy@...