Mercury Exposure from Thimerosal Significantly Associated with Abnormal Brain Connectivity

by | Jul 24, 2018 | 2017, Brain Health, Pharmaceutical Hazards, Vaccines

Written by Angeline A. De Leon, Staff Writer. Results from this study suggest that Hg exposure from thimerosal is significantly associated with the ACSDs of ASD, TD, and ADD/ADHD.

brain healthWhile classified as disparate conditions under the general category of neurodevelopmental disorders, autism spectrum disorder (ASD), tic disorder (TD), and attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD) share common neuropathology and symptomology1. Emerging research showing evidence of a similar pattern of abnormal brain connectivity (representing the coherence of different brain regions) among these disorders2 suggests a potential need to re-conceptualize these neurodevelopmental conditions as subsets of what has been termed abnormal connectivity spectrum disorder (ACSD). ACSD is hypothesized to involve some type of neuronal insult, including those related to neurotoxicity, neuroinflammation, oxidative stress, etc., which might result in increased short-range connectivity and reduced long-range connectivity1. Mercury is a well-known environmental neurotoxicant associated with a similar pattern of neuropathological change in brain connectivity, and increasing evidence suggests a link between mercury exposure and long-term risk of ASD, TD, and ADD/ADHD3. Due to routine administration of thimerosal, a mercury-based antiseptic and antifungal agent, as part of childhood vaccination, reports estimate that children may receive more than 50% of their mercury exposure from vaccination procedures4. When combined with environmental mercury exposure, it is not uncommon for some children to exceed the safety limits of total mercury dosage established by the US Environmental Protection Agency5. Epidemiological studies now suggest a dose-dependent relationship between exposure to mercury from thimerosal-containing hepatitis B vaccines and significantly elevated risk of neurodevelopmental disorders6. Given strong evidence of the potential relationship between mercury exposure and child risk of ASD, TD, and ADD/ADHD, Geier and colleagues at the Institute of Chronic Illnesses (2017) conducted a prospective assessment looking at whether cases of ACSD diagnoses would be associated with higher doses of mercury exposure from thimerosal-containing influenza vaccines administered to children.

Using a prospective, longitudinal, case-control study design, data from a cohort of over 1.95 million children was analyzed as part of a project linking medical event information, vaccine history, and select demographic information from computerized databases. Inpatient and outpatient diagnoses from the population were reviewed according to the International Classification of Diseases, and children receiving at least one diagnosis of ASD, TD, or ADD/ADHD were considered to have ACSD. Children whose vaccine files indicated that they received mercury exposure from thimerosal-containing Haemophilus influenzae type b (Hib) vaccines (25 µg mercury per dose) during the first 15 months of life were considered case outcomes. Children diagnosed with febrile seizures, unspecified metabolic disturbances, or cerebral degenerations (conditions not plausibly biologically linked to thimerosal) were considered control outcomes.

Analyses revealed that cases diagnosed with ASD (Odds Ratio = 1.493 per 25 µg mercury exposure, 95% Confidence Interval = 1.349-1.627), TD (OR = 1.428 per 25 µg mercury exposure, 95% CI = 1.256-1.600), or ADD/ADHD (OR = 1.503 per 25 µg mercury exposure, 95% CI = 1.425-1.582) were significantly (p < 0.001 for all) more likely than controls to have received mercury exposure from Hib-containing vaccines administered during the first 15 months of childhood. Sub-analyses based on gender followed a similar dose-dependent association (on a per 25 µg mercury basis) for both males (ASD OR = 1.479, TD OR = 1.424, ADD/ADHD OR = 1.518; p < 0.001 for all) and females (ASD OR = 1.517, TD OR = 1.428, ADD/ADHD OR = 1.453; p < 0.001 for all).

Consistent with previous epidemiological studies, findings confirm a significant, dose-dependent relationship between increased mercury exposure from thimerosal-containing childhood vaccines and risk of ACSD diagnosis. While routine childhood immunization can serve as a potentially life-saving protocol, data suggest that it may be beneficial to limit use of vaccines containing high doses of thimerosal. To extend current findings on ACSD, it would be valuable to examine the direct effects of mercury on brain connectivity using neuroimaging techniques.

Source: Geier DA, Kern JK, Homme KG, et al. Abnormal brain connectivity spectrum disorders following thimerosal administration: a prospective longitudinal case-control assessment of medical records in the vaccine safety datalink. Dose-Response: An International Journal. 2017; 15(1): 1-12. DOI: 10.1177/1559325817690849.

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Posted July 24, 2018.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

References:

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