One of the points that anti-vaccine proponents keep bringing up is how autism prevalence has been going up over the past few decades. They notice how autism diagnoses have gone up and correlate that with an expanded vaccine schedule, then finally make the leap to imply it was the vaccines that caused autism. When we say that an expanded definition and expanded surveillance is what has in big part resulted in the increase, they laugh it off. That is not possible, they say; the increase must be a real increase of actual cases.
Recently, a new study came out of South Korea. It was a 5 year study that looked at all children in a South Korean community, not just high risk kids, or those that went to the doctor. They found an Autism Spectrum Disorder (ASD) prevalence rate of 2.6%. By comparison the current rate is estimated to be 1/110 or 0.9%. By looking at all children, vs. just those in the high risk groups, as has been the practice generally, the prevalence rate almost tripled.
This is a perfect example of how increased surveillance can result in an increase in number of diagnoses. It would be insane to imply that the real rate of ASD cases tripled while the authors did the study. As Steve Novella has said this is literally a case of casting a wider net with smaller holes, more specifically in this case by casting a wider net. This study lends support to what we in the pro-health community have been saying for a while now: that expanded diagnostic criteria coupled with more awareness and increased surveillance are the likely contributors to the perceived increase in ASD rates in recent history.
Autism diagnoses rates have been going up steadily, but have autism incidence rates gone up, or is this increase due just to us being more aware, looking for it more and expanding the diagnostic criteria? Or is it both an actual increase due to some factor and the wider net with smaller holes? I do not pretend to know the answer. If only anti-vaxers were as humble.