What’s Going On? The Question Of Time Trends In Autism

“The rising incidence of autism should be a matter of urgent public concern”

Public Health Reports, Volume 119, Issue 6, Pages 536-551 (November 2004) The complete paper is available without charge at this address:

Mark F. Blaxill


Increases in the reported prevalence of autism and autistic spectrum
disorders in recent years have fueled concern over possible environmental

The author reviews the available survey literature and finds evidence of large increases in prevalence in both the United States and the United Kingdom that cannot be explained by changes in diagnostic criteria or improvements in case ascertainment.

Incomplete ascertainment of autism cases in young child populations
is the largest source of predictable bias in prevalence surveys; however,
this bias has, if anything, worked against the detection of an upward trend in
recent surveys.

Comparison of autism rates by year of birth for specific geographies provides the strongest basis for trend assessment.

Such comparisons show large recent increases in rates of autism and autistic spectrum disorders in both the U.S. and the U.K.

Reported rates of autism in the United States increased from ,3 per 10,000 children in the 1970s to .30 per 10,000 children in the 1990s, a 10-fold increase.

In the United Kingdom, autism rates rose from ,10 per 10,000 in the 1980s to roughly 30 per 10,000 in the 1990s.

Reported rates for the full spectrum of autistic disorders rose from the 5 to 10 per 10,000 range to the 50 to 80 per 10,000 range in the two countries.

A precautionary approach suggests that the rising incidence of autism should be a matter of urgent public concern.

Note: The editor of PHR offered this poignant introduction: One article, by Mark Blaxill, reviews the question of temporal trends in the frequency of autism. It is from a different vantage point than most other articles on the subject, including ones we have run in the Journal, but he puts forth a well-reasoned position. It is also a good reminder why many of us picked public health as our career choice.

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