One Review Investigates Aluminum’s Tie to Neurodevelopmental Disorders; the Other Investigates Its Relationship to Asthma
An international team of researchers recently released a review that examined the relationship between neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD), schizophrenia, and bipolar disorder with early life exposures to aluminum-based adjuvants (ABAs). The review investigated the current knowledge regarding the role of early inflammation, dysfunction in the immune system, and autophagy, a critical neurodevelopmental process involving synaptic pruning, that ABAs may impact. Although the researchers examined NDDs, this new study mainly focused on ASD. The authors referenced recent ASD research suggesting that the immune system is a convergence point between ASD-related genetic and environmental risk stressors. They also pointed to environmental influences that affect the maternal, fetal, and/or neonatal immune pathways, which could cause neuroimmune alterations in a developing infant. The researchers added that immune system activation from exposure to external pro-inflammatory compounds during critical periods could cause permanent effects and increase the risk of NDDs. The authors then discussed ABA exposure during the first months of life through ABA-containing vaccinations. They identified two risk factors: direct aluminum particle toxicity to immune and nervous systems and adverse effects caused by the adjuvant’s activation of immune responses during critical periods of development. The team found evidence that autophagy is likely to be disrupted in the ASD brain and that this disruption could impair ABA clearance. They also suggested that ABAs are persistent pro-inflammatory particles in the early environment of infants and that ABAs may enter the brain due to an immature blood-brain barrier, altering the autophagy process and promoting neuroinflammation. The authors concluded that since there is no proof that ABAs are entirely safe to use in children, they believe that further research should be conducted investigating a potential link between ABAs and NDDs, including:
- Epidemiological studies comparing different vaccination schedules and ABA exposure in children;
- Genetic studies of populations at risk, potentially targeting candidate genes in immune and autophagy pathways;
- Pharmacokinetics and pharmacodynamics of ABAs during both pre- and postnatal periods in animal models;
- Fundamental immunological data to better understand the mechanisms of immune action of ABAs, in addition to their possible capacity, to induce neuroinflammation and alterations of immune-neural interactions during early postnatal life, e.g., using autophagy-deficient mouse models.
In a related story, a research group funded by the CDC has found a potential increase in childhood asthma among children exposed to ABAs in the first few years of life. The authors say their results are preliminary and should not lead to changes in vaccination practice. Interestingly, there is a higher rate of asthma among children with autism. This retrospective cohort study used the Vaccine Safety Datalink (VSD) to gather vaccination histories of 326,991 children born between 2008 and 2014. A positive association was found between cumulative vaccine-associated aluminum before age 24 months and persistent asthma at age 24 through 59 months among children with and without eczema. When vaccine-associated aluminum was investigated as an acute exposure, a small positive association was discovered for children without eczema. Secondary analyses with more restrictive inclusion criteria and smaller sample sizes showed positive associations in some of the analyses, but not all. First author Matthew Daley states, “The incidence of persistent asthma in children less than 5 years of age is about 3.8%, and there are different estimates from different data sources. So if these study findings are replicated in other studies, the implication is that reducing aluminum could reduce asthma risk below 3.8%. By how much is difficult to say, because asthma has many environmental triggers.”
