Photo of an old cannister of DDT
Scientists say they have established, for the first time, a link between the pesticide DDT and the development of Alzheimer's later in life

DDT exposure linked to Alzheimer’s disease

30 January, 2014

Natural Health News — Scientists have known for more than 40 years that the synthetic pesticide DDT is harmful to bird habitats and a threat to the environment.

Now a team of researchers from Rutgers University, Emory University and the University of Texas, say exposure to DDT – banned in the United States since 1972 but still used as a pesticide in other countries – may also increase the risk and severity of Alzheimer’s disease in some people, particularly those over the age of 60.

The study, published online in JAMA Neurology, showed that levels of DDE, the chemical compound left when DDT breaks down, were higher in the blood of late-onset Alzheimer’s disease patients compared to those without the disease.

DDT was introduced as a pesticide during WWII and used in the United States and elsewhere for insect control in crops and livestock and to combat insect-borne diseases like malaria.

This study claims to be the first to link a specific chemical compound to Alzheimer’s disease and, say the researchers, we urgently need to know more about how DDT and DDE may trigger neurodegenerative diseases such as Alzheimer’s.

Pay attention to environmental causes

Commenting on the findings one of the authors, Jason R. Richardson, associate professor in the Department of Environmental and Occupational Medicine at Rutgers’ Robert Wood Johnson Medical School and a member of the Environmental and Occupational Health Sciences Institute (EOHSI) said:

“I think these results demonstrate that more attention should be focused on potential environmental contributors and their interaction with genetic susceptibility. Our data may help identify those that are at risk for Alzheimer’s disease and could potentially lead to earlier diagnosis and an improved outcome.”

Although the levels of DDT and DDE have decreased significantly in the United States over the last three decades, the toxic pesticide is still found in 75-80% of the blood samples collected from the Centers for Disease Control and Prevention. This occurs because the chemical can take decades to breakdown in the environment.

In addition, people may be exposed to the pesticide by consuming imported fruits, vegetables and grains where DDT is still being used and eating fish from contaminated waterways.

More DDE in the blood

In the study 74 out of the 86 Alzheimer’s patients involved – whose average age was 74 – had DDE blood levels almost four times higher than the 79 people in the control group who did not have Alzheimer’s disease.

Brain cell studies found that DDT and DDE increased the amount of a protein associated with plaques (called amyloid proteins) believed to be a hallmark of Alzheimer’s disease.

These sticky plaques – which may form in regions of the brain involved in memory, learning and thinking – break off and clump together in the brain and increase as the disease progresses.

This new research is important, Richardson says, because it suggests that DDT and DDE may directly contribute to the process of plaque development. “We need to conduct further research to determine whether this occurs and how the chemical compound interacts with the ApoE4 gene” Richardson says.

Beyond genetics

The scientists also found that patients with a version of ApoE gene (ApoE4), which greatly increases the risk of developing Alzheimer’s, and high blood levels of DDE showed even more severe cognitive impairment than those without this gene.

Although the exact cause of Alzheimer’s disease is not known, scientists believe that late-onset Alzheimer’s may be linked to a combination of genetic, environmental and lifestyle factors. Much of the research into Alzheimer’s and other neurodegenerative diseases has mostly been centred on finding genetic connections, Richardson says.

“This study demonstrates that there are additional contributors to Alzheimer’s disease that must be examined and that may help identify those at risk of developing Alzheimer’s,” says Richardson. “It is important because when it comes to diagnosing and treating this and other neurodegenerative diseases, the earlier someone is diagnosed, the more options there may be available.”

Not the first study to find this link

Although this may be the first study to specifically link DDT with Alzheimer’s – it is not the first study to link pesticide exposure with this and other related neurodegenerative diseases. Indeed, the association is well established.

A 2011 review by Spanish researchers, for example, found that the prevalence and the risk of having Alzheimer’s disease, Parkinson’s disease, multiple sclerosis and suicide were significantly higher in districts with greater pesticide use as compared to those with lower pesticide use. Another in 2010 which focused on an agricultural community in Utah found that the incidence of Alzheimer’s and dementia rose 42% in those who had occupational exposure to pesticides. A 2001 study in Canada found that occupational exposure to fumigants and/or defoliants raised the risk of Alzheimer’s disease more than four-fold.

In addition, the pesticides known as neonicotinoids (or neonics) have been shown to give bees a kind of Alzheimer’s, which is believed to contribute to their fatal effects in our pollinators.