Tuesday, October 6, 2009

Correlation or Casual Relation?

There are two correlations that have been picking at my brain for some time now. Vaccinations and autism and the much lesser known one about the flu and schizophrenia. About twenty years or so after a major flu outbreak (most notably the Spanish Flu of 1918) there is an increase in the incidence (rate of occurrence of new cases) of schizophrenia.

Correlations do not imply a casual relation. The argument for a casual relation between the flu and schizophrenia is well, to put it bluntly, pretty much laughed at by the scientific community. Regardless of how ridiculous the proposal of a casual link might be, there is no denying the correlation. However, when it comes to vaccines and autism there is a growing acceptance of there being an actual causal relation not just a correlation. Something that was once considered ridiculous. (Of course, mercury is safe!)

Let's start with some undisputed facts about thiomersal, the mercury compound used as a preservative in vaccines.

(1) The use of thiomersal in routine childhood vaccines is being phased out in the United States and the European Union.
(2) Thiomersal is used in inactive flu vaccines in children two years and older and in other vaccines that are not routinely recommended (emphasis mine) in young children, including the vaccine for diphtheria and tetanus, according to the Center for Biologics Evaluation and Research of the U.S. Food and Drug Administration.
(3) Thiomersal is metabolized into ethyl-mercury
and thiosalicylate in the body.
Ethylmercury clears from blood with a half-life of about 18 days. (Half-life is the period of time it takes, for a substance undergoing decay, to decrease by half.) So, at 18 days 50% of the ethylmercury that was already metabolized and present in the blood stream is gone. At 36 days 25% of the original amount of metabolized ethyl-mercury remains, at 54 days 12.5% remains, etc.
(5) Ethyl-mercury in the brain has a half-life of about 14 days. So, at 14 days 50% remains, 28 days 25%, 56 days 12.5%, etc.
(6) Inorganic mercury metabolized from ethyl-mercury has a much longer clearance, at least 120 days. (Emphasis added.)
(7) Ethyl-mercury is very permeable, meaning it flows pretty much unhindered throughout the body, it crosses through the blood-brain barrier (not very easy) and the placental barrier (actually very easy, hence women are so heavily cautioned against consuming certain foods and medications during pregnancy, almost everything can cross the placental barrier).
(8) Using thiomersal allows for multi-dose vials of vaccines instead of single-dose which are more expensive.
(9) Thiomersal's safety for its intended uses first came under question in the 1970s, when case reports demonstrated potential for neurotoxicity when given in large volumes as a topical antiseptic.

While thiomersal and autism remain a controversy, but we do know that mercury, as well as other heavy metals, causes serious medical problems in high enough doses. It is important to note that the effects of
mercury poisoning are partially dependent on which type of mercury, elemental mercury, inorganic mercury compounds (as salts), or organomercury compounds that the individual was exposed to.

The empirical evidence and date on thiomersal just isn't there for either case. Why? Because it is studied very little to not at all. Methyl-mercury has been studied rather extensively, but thiomersal breaks down into ethyl-mercury.

Perhaps this is overly cynical, but there is little financial incentive to study thiomersal and the autism correlation. If thiomersal is casually linked to autism, there would be a huge public outcry. There would be an increase in lawsuits against pharmaceutical companies, a drop in sales, a huge mistrust of vaccines in general, a decrease in the number of people who get vaccinated (regardless of what it is for) and which vaccines they do get (if any) and a large decrease in reveune for drug companies. Also, quite probably an increase of indiences of diseases that formerly were vaccinated against. The government would also come under fire since the FDA approved the vaccines in the first place. So, in light of all that who would (1) want to study it and (2) actually get funding for it? And for the cynics, like myself, (3) manage to not have their results buried?

Although, as thiomersal is eliminated from vaccines and/or individuals start refusing to get vaccines that contain thiomersal, if there is a decrease in the incidence of autism... Well, such a correlation kind of just fuels the fire now, doesn't it?