February 11, 2021
Veterans who were exposed to the herbicide Agent Orange during the Vietnam War may be at increased risk of developing dementia compared to fellow soldiers who were not exposed. The results raise worrisome concerns, since many Vietnam veterans are now in their late 60s and 70s, an age when diagnoses of Alzheimer’s disease start to become increasingly common. The findings also raise potential concerns about how environmental toxins may play a role in brain ailments, including Alzheimer’s disease, the most common type of dementia in the world.
U.S. forces used Agent Orange during the Vietnam War to defoliate jungle trees and plants that provided cover for enemy forces, and to kill food crops. Many American servicemen were exposed to the defoliant during the war, most likely to very high doses, and its active ingredient dioxin, may persist in fat tissues in the body for decades.
Previous research has linked Agent Orange to neurologic ailments like Parkinson’s disease, various cancers, Type 2 diabetes, hypertension and other diseases. An earlier study suggested that Agent Orange might also be linked to a slightly increased risk of dementia, but this study, published in JAMA Neurology, was much larger.
For the current study, researchers at Johns Hopkins School of Medicine reviewed health records of more than 300,000 veterans, 38,121 of whom had been exposed to Agent Orange. They tracked their health, beginning when most were in their early 60s, for up to 14 years.
They found that veterans exposed to the herbicide were nearly twice as likely to be diagnosed with dementia than their veteran peers who hadn’t been exposed.
Among those who developed dementia, those who had been exposed to Agent Orange were also likely to be diagnosed at a younger age: 67.5 years on average, versus 68.8 years for those who hadn’t been exposed.
The study showed only a link and could not prove cause and effect. But the study was large and suggested the dementia risk was strong.
The researchers aren’t sure why Agent Orange might increase dementia risk. One possibility is that the dioxin in Agent Orange might interrupt hormones and brain neurotransmitters.
The authors note that many factors can contribute to who gets dementia, including genetic factors, diet, stress levels, exercise levels and more. Still, Vietnam vets who were exposed to Agent Orange want to be extra vigilant about early signs of cognitive problems or possible dementia.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Steven Martinez, BS; Kristine Yaffe, MD; Yixia Li, MPH; et al: “Agent Orange Exposure and Dementia Diagnosis in US Veterans of the Vietnam Era.” JAMA Neurology, January 25, 2021