Monday, October 5, 2009

Conflicting Studies, Good/Bad Science

Time magazine has two stories on autism diagnostic rates. One report is on a careful census of adults, trying to determine if there is a real difference between generations. The second report is on a telephone survey that shows a sudden spike in rates based on poorly worded questions. I never trust phone surveys -- they have numerous validity issues.

Article 1:

For the First Time, a Census of Autistic Adults
By CLAUDIA WALLIS Saturday, Oct. 03, 2009

On Sept. 22, England's National Health Service (NHS) released the first study of autism in the general adult population. The findings confirm the intuitive assumption: that ASD is just as common in adults as it is in children. Researchers at the University of Leicester, working with the NHS Information Center found that roughly 1 in 100 adults are on the spectrum — the same rate found for children in
England, Japan, Canada and, for that matter, New Jersey.

Article 2:

New Study Sees a Higher Rate of Autism: Is the Jump Real?
By CLAUDIA WALLIS Monday, Oct. 05, 2009

Experts not involved in the study caution that parent surveys are not the gold standard for measuring the prevalence of a medical condition. "The fact that 40% of the parents reporting that their child had received an ASD diagnosis now say the child no longer met criteria does suggest that there may be over-reporting in this survey," says Craig Newschaffer, a leading autism epidemiologist at Drexel University School of Public Health.

The first story includes the following information:

This finding [of similar rates] would also appear to contradict the commonplace idea that autism rates have exploded in the two decades. Researchers found no significant differences in autism prevalence among people they surveyed in their 20s, 30s, 40s, right up through their 70s. "This suggests that the factors that lead to developing autism appear to be constant," said Dr. Terry Brugha, professor of psychiatry at the University of Leicester and lead author of the study. "I think what our survey suggests doesn't go with the idea that the prevalence is rising."

This makes intuitive sense to me. Of course, the media like the narrative of a sudden spike in any disease. Suddenly, we have a CSI-style mystery to solve. Someone must be to blame! Government and industry are hurting our children! (Forget that life expectancy keeps increasing and most measures of "health" are improving over the decades.)

I can already predict which study will make the nightly news, cable chat shows, and Web sites.