Sunday, October 03, 2004

Eat Your Mercury

Yes, studies show that a known neurotoxicant is not associated with problem developmental outcomes, but rather has a progressively protective effect within the range of exposures sourced to vaccines. This report of two studies published in Pediatrics suggests just how little faith we should put in all the population studies of thimerosal and outcomes.

The emerging consensus is that autism is epigenetic -- a genetically determined subset of the population is vulnerable to an increasing set of environmental exposures. So don't be snowed by non-science like this.

Instead, look at Madeline Hornig's study in Molecular Psychiatry, June 2004.


Mercury-Containing Vaccines Have Salutary Effects in Children

NEW YORK (Reuters Health) Sept 17 - Immunizing infants with vaccines containing the preservative thimerosal may actually be associated with improved behavior and cognitive outcomes, according to two British studies published in the September issue of Pediatrics.

It has been hypothesized that ethylmercury contained in thimerosal-preserved vaccine is associated with developmental disorders in young children. The Institute of Medicine recently released the last in a series of reports concluding that there is no such link. However, many individuals remain unconvinced that the agent is safe.

Dr. Jon Heron of the University of Bristol, and colleagues prospectively followed 12,956 children, born in 1991 and 1992, until they were 91 months old. Data was collected on doses of thimerosal-containing diphtheria/tetanus/pertussis vaccines given at ages 3, 4, and 6 months, as well as on measures of behavior, fine motor skills, speech, tics and special education needs.

Instead of finding that outcomes were worse with increasing exposure to thimerosal, the authors observed significant inverse associations between exposure and hyperactivity at 47 months, conduct problems at 47 months, motor development at 6 months and at 30 months, difficulties with sounds at 81 months, speech therapy, special needs and other difficulties and disabilities,

After adjusting for potential confounders, such as birth weight and maternal education, there was only one marginally significant finding that linked exposure by the age of 3 months with "poor prosocial behavior" at 47 months. Otherwise, of 69 statistical tests performed, eight outcomes suggested a more beneficial outcome as a result of increased exposure.

In the second report, Dr. Nick Andrews of the Communicable Disease Surveillance Centre, London and colleagues conducted a retrospective cohort study involving 107,152 children born between 1988 and 1997.

In analyses adjusted for gender and year of birth, there appeared to be protective effects from thimerosal-containing vaccine exposure for general developmental disorders, attention-deficit disorder, and unspecified developmental delay.

The only condition associated with increased risk with increasing thimerosal exposure was tics. However, "the vast majority of tics were minor transient events," the authors note.

Hence, they conclude that "there is no reason to change current immunization practices with thimerosal-containing vaccines on grounds of safety."

Pediatrics 2004;114:577-591.