Here at Applied Behavioral Strategies, the mission is to improve the quality of life through effective intervention. One way we hope to do that is by reviewing research articles for our readers. Today’s article has actually been the topic of a lot of social media. See these headlines here and here and a reader actually wrote in about it on Monday.
Do pregnant women who get the flu or a fever actually increase the likelihood that their child will get autism? Let’s find out by actually reading the research.
The journal called Pediatrics published this study and Hjördis Ósk Atladóttir, Tine Brink Henriksen, Diana E. Schendel and Erik T. Parner authored the study. A quick search on Medline reveals that Dr. Atladóttir is chasing this topic of autism trying to find something to explain how it develops. He published a similar paper in 2010 in the Journal of Autism and Developmental Disorders. In that paper, he discussed pregnant women who had been hospitalized and later had a child with autism. He has published on cytokine levels and autism, patterns of contact with hospitals and autism, and family history of autoimmune disease and autism.
Purpose of the Study
The authors set out to “assess the association between self-reported common infections and autism in the child“. The authors clearly state that they estimated an association. Yet, when this study hit the news, reporters and scientists discussing the study omitted these little details.
The sample. The authors used an existing data base to gather their data (Danish National Birth Cohort). The authors selected 31% of the cohort for their data analysis.
The data collection. All the interview questions asked to the mothers occurred during the initial cohort recruitment completed by different researchers. These authors did not have contact with the mothers. Interestingly, the authors actually reported that “there was no specific question regarding respiratory disease and influenza”. It should make you wonder how they “estimated” the results of their highly disseminated “study”. In fact, the researchers actually asked the mothers, “did you take an antibiotic?” The authors clarified further, “The questionnaire did not include a question concerning the direct disease indication for the antibiotic use”. Wow! Yet all the media around this paper specifically said “flu”.
Data facts. Only 1% of the sample actually reported having the flu. Compare that to the percent of women with other issues: fever (24%), antibiotic use (19%), yeast infection (19%), cystitis (12%) and urinary tract infection (12%). Another interesting fact is that the researchers compared maternal responses during interviews with data from hospital records (e.g., diagnosis at discharge). The authors state, “The overall agreement between maternal reports of infection episodes and a corresponding hospital contact record was fairly good for most infections” (e.g., cystitis, pyelonephritis, and vaginal yeast infection). However, the authors also noted that “there was a very low agreement between maternal-reported infection and hospital-registered infection when the self-reported information was retrieved from open-ended questions” (e.g., flu). Thus, it seems that the likelihood the mothers really had the flu when they reported that they did, is actually quite low.
Data analysis. The authors used statistical analysis to determine if any relationships between the variables existed. What the media did not cover in reporting this study, is the important fact that the authors examined relationships between illnesses and any form of autism spectrum disorder as well as any relationship between diseases and infantile autism.
The authors reported a number of results, most of which had no statistical significance. The authors noted that a statistically significant difference was found among mothers who self-report the flu (be sure to see the note above regarding the accuracy of reporting) and went on to have a child with autism. Specifically, out of the entire sample, only about 800 mothers reported having the flu. Of those, only 9 went on to be diagnosed with an autism spectrum disorder. This is hardly reason for alarm especially since we are having autism diagnosed at a rate of 1 in 86!
The authors noted that another statistically significant association was found between mothers who had a fever longer than 7 days. The number of women with a fever episode was quite high 23, 027). The number of them who went on to have a child with infantile autism was 101. Again, this hardly seems reason for alarm given the staggering rate of autism. Finally, the number of women who had a fever lasting longer than 7 days was 1361. Of those, only 14 went on to have a child diagnosed with infantile autism.
The authors found similar associations with antibiotic use. Again, the numbers are not alarming given the overwhelming rate of autism.
The key statement in the discussion section should be highlighted: “There was little evidence that self-reported common infections during pregnancy are risk
factors for ASD in the child”
Can someone explain how the media complete twisted this in to a “flu during pregnancy increases the risk of autism” headline?
The authors did go on to talk about their previous work on this topic, ” We reported in our previous study that viral infection during the first trimester gave rise to an almost threefold increased risk of ASD“.
Side note: We all know that the flu is a virus. But isn’t the vaccine for the flu a live virus? Let’s see what the CDC has to say about it. Well, I’ll be darned, it appears that the nasal spray is a live virus. “Live, attenuated influenza vaccine (LAIV) contains live but attenuated (weakened) influenza virus. It is sprayed into the nostrils“. The CDC goes on to say that pregnant women should not take the live virus spray.
This study is full of methodological errors. Yet, Pediatrics continue to publish it and the media continue to twist the findings. Please, before you believe the “latest medical study”, you might find it more helpful to actually read the study rather than believe what someone tells you about the study.
The Elephant in the Room
So, if the researchers had access to all this data, why didn’t they ask better research questions? Why didn’t they look for associations between women who got the flu vaccine and still got the flu? Or how about this one: “does getting the flu shot increase the likelihood of your child getting autism?” There is so much more that could be asked, yet these researchers did not seem interested. Maybe it wasn’t the “politically incorrect” thing to do.