EBD Blog

Last month when I first saw the title “Thimerosal exposure in infants and neurodevelopmental disorders: An assessment of computerized medical records in the Vaccine Safety Datalink,” I was initially skeptical, but I wanted to check what was being proposed, so I jumped right past the author list and read the abstract. I was a bit intrigued, thinking to myself, “Hmmm…maybe there’s more to this than I thought.” Then, when I went to locate the actual article, I realized that the second and third authors were the Geiers, David and Mark. Slowed by the connection, I put the study aside for later review. Now, others have already done the analysis for me, and those analyses are the focus of this entry.

First, here’s the abstract and citation:

Young HA, Geier DA, Geier MR.
The George Washington University School of Public Health and Health Services, Department of Epidemiology and Biostatistics, United States.
The study evaluated possible associations between neurodevelopmental disorders (NDs) and exposure to mercury (Hg) from Thimerosal-containing vaccines (TCVs) by examining the automated Vaccine Safety Datalink (VSD). A total of 278,624 subjects were identified in birth cohorts from 1990-1996 that had received their first oral polio vaccination by 3 months of age in the VSD. The birth cohort prevalence rate of medically diagnosed International Classification of Disease, 9th revision (ICD-9) specific NDs and control outcomes were calculated. Exposures to Hg from TCVs were calculated by birth cohort for specific exposure windows from birth-7 months and birth-13 months of age. Poisson regression analysis was used to model the association between the prevalence of outcomes and Hg doses from TCVs. Consistent significantly increased rate ratios were observed for autism, autism spectrum disorders, tics, attention deficit disorder, and emotional disturbances with Hg exposure from TCVs. By contrast, none of the control outcomes had significantly increased rate ratios with Hg exposure from TCVs. Routine childhood vaccination should be continued to help reduce the morbidity and mortality associated with infectious diseases, but efforts should be undertaken to remove Hg from vaccines. Additional studies should be conducted to further evaluate the relationship between Hg exposure and NDs.

Young, H. A., Geier, D. A., & Geier, M. R. (2008). Thimerosal exposure in infants and neurodevelopmental disorders: An assessment of computerized medical records in the Vaccine Safety Datalink. Journal of Neurological Sciences, 2008 May 14.

Barbara Martin, M.D., a neurologist who worked for a while in continuing medical education before taking up writing full time about medical matters at Pathophilia, published an extended set of posts analyzing the paper. Dr. Martin posted observations about IRB approval and follow-up, commentary on the pharmacology in the introduction, notes about neuropsych and the methods, analyses of the results, and comments on the discussion. Similarly, Epi Wonk published a series on the Young et al. study; he demonstrated how the data of the study appear to have been imputed (inferred) using questionable methods and assumptions (”This is just not done. It’s not valid. It’s not ethical. Adding imaginary cases into a data set borders on scientiific fraud.”), explained how the data Young et al. analyzed are very likely confounded by the rising rates of identification of children with Autism, and clarified the basic nature of the study (its an analysis of data gathered at the level of groups, not data about individuals).

These analyses are quite thoughtful and thorough. Reading them is like taking a class on analyzing research papers. Take the hour of so required to read them.