Numbers don’t add up in autism/epilepsy study
The Journal of Child Neurology published results from research on donated brain tissue from the Autism Speaks Autism Tissue program. The study found that people with both autism and epilepsy had a higher death rate than those with autism alone. 39 percent of donors to the tissue program had epilepsy, higher than the estimated rate of epilepsy in the general autism population. The study authors also examined data from the California State Department of Developmental Services, and found that people with both conditions have an 800 percent higher death rate than those with autism alone. A neurologist and member of the Autism Speaks Scientific Advisory Council suggested that both the autism and epilepsy communities should be motivated by this information to increase understanding of common risk factors and mechanisms of both conditions. The story, while short, has been picked up by multiple news outlets and blogs based on a Google news search I conducted.
The most glaring piece of information that must be examined is the 800 percent gap in the death of rate of autistics and autistics with epilepsy. While that may sound alarming, news outlets and study publishers will often relay statistics in that format as a means of generating attention. That doesn’t mean the information is false, but such margins can still be dramatized (another way news writers will dramatize such a stat is saying “eight times as likely”). When it comes to death rates, the overall percentage can never go beyond 100 for any particular category (and all living organisms eventually die). Unfortunately, not enough constants are given in any news article on this story for me to make a statistic that is less misleading. We don’t know what the death rate means, but based on the data presented by California’s Department of Developmental Services, we can make an educated guess that the death rate in this study refers to a specific point in the lifespan, and that the death rate is relatively low.
In fact, to obtain 100 percent using a multiplier of 800, the death rate of people with autism alone could be no more than .125, an eighth of one percent. It’s safe to say both figures are far lower than that with what I can deduce based on the information presented. In other words, there’s little statistical evidence to be highly alarmed by these findings because news articles did not provide any base percentages to work with. While that would certainly kill a story’s emotional impact, it would also kill any chance the story could be interpreted as a cause for panic. To add mathematical insult to injury, we’re not given the estimate of epilepsy overlapping with autism from the Autism Speaks tissue donation program.
I do not know any autistic people with epilepsy, but a colleague of mine did suffer from an epileptic episode in college. As the two of us live with the experiences of our respective conditions, it can be difficult when stories like this surface and leave out a few minor details that wouldn’t take much time to procure. Either reporters didn’t bother to review the study carefully, or the study itself did not include any base numbers in its findings. While deadlines and space are always the bane of reporters, one task that’s prided on is the ability to provide information so the audience doesn’t have to spend time or resources doing the same.
However, this may also serve a lesson on learning common mathematical functions. Journalists have an old adage about running away from math because that skill isn’t needed for all stories, but crunching numbers is valuable to put stats in perspective, which this story lacks. Calculus isn’t required, but it won’t hurt you to convert numbers into percentages, fractions, averages and so forth.