Evidence linking agent orange, parkinson's, heart disease "limited or suggestive", report


Evidence linking agent orange, parkinson's, heart disease


Writers of a new report found "limited or suggestive evidence" that exposure to Agent Orange and other chemicals used in the Vietnam War is linked with an increased risk of developing ischemic heart disease and Parkinson's disease for veterans of that war.

From 1962 to 1971 US forces sprayed herbicides all over Vietnam. The aim was not just to strip away the jungle canopy under which enemy forces could hide, but also to destroy crops they might rely on and to clear areas around US bases of tall grasses and bushes.

While most of the spraying was done from planes and helicopters, some smaller-scale operations were carried out from boats and ground vehicles and by soldiers on foot using spraying equipment that they carried on their backs.

Under a 1991 act the Institute of Medicine (IOM) is mandated by Congress to report every two years on the latest evidence about the health effects of the Vietnam War herbicides including the highly toxic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCCD, code named Agent Orange).

The reports are sponsored by the US Department of Veterans Affairs. Update 2008 is the 8th such report and was released on 24th July. According to an announcement on the IOM website:

"The authoring committee found suggestive but limited evidence that exposure to Agent Orange and other herbicides used during the Vietnam War is associated with an increased chance of developing ischemic heart disease and Parkinson's disease for Vietnam veterans."

Ischemic heart disease is when the heart does not get enough blood and can lead to heart atttack and stroke. It is the leading cause of death among people in developed countries and major risk factors include buildup of cholesterol in the arteries, age, smoking, high blood pressure, and diabetes.

Parkinson's disease is caused by a chronic and progressive disease of the brain due to loss of nerve cells that secrete dopamine. It affects about 1 in 100 people over the age of 60, which is around 5 million people worldwide.

As Parkinson's disease advances the person's movements become rigid, shaky and their speech is impaired. The disease also affects ability to think and remember, language, and can also trigger depression. In extreme cases there can be complete loss of movement.

According to a commentary from the National Academy of Sciences (NAS), this latest finding means the evidence shows there could be a link between exposure to Agent Orange and the two diseases, but it is not clear cut because the studies on which it is based conflict with each other, there are problems with their design, and whether other factors were sufficiently accounted for.

Before this latest report the cumulative evidence was not good enough to say this, said the NAS.

The report authors reviewed several studies looking at links between TCCD exposure and heart disease, and many of these found greater incidence of disease was associated with greater exposure to the chemical.

However, they also found several flaws in the studies. For example, the studies did not entirely account for the possible impact of smoking, age, weight, and other well known risk factors.

But because of the volume of evidence, and now the emergence of new biological data showing the possible mechanisms by which TCCD might be able to cause heart disease, the authors of the IOM report concluded that veterans exposed to TCCD during the Vietnam War might be at higher risk of heart disease.

For potential links with Parkinson's disease the IOM report authors looked at 16 studies that examined herbicide exposure in people with Parkinson's or diseases with symptoms similar to Parkinson's. They also looked at studies that have examined the possibility that risk factors for Parkinson's might include exposure to compounds similar to TCCD and other Vietnam War herbicides.

The authors called for more studies on links between Parkinson's and herbicide exposure, particularly ones that look at the relationship between Parkinson's and Agent Orange exposure among veterans.

"Veterans and Agent Orange: Update 2008."

Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides (Seventh Biennial Update), Institute of Medicine.

ISBN-10: 0-309-13884-1

ISBN-13: 978-0-309-13884-0

Source: National Academy of Sciences, IOM.


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Section Issues On Medicine: Retirees