Pollutants may speed up ALS progression
02 March, 2019
New research, appearing in the BMJ Journal of Neurology, suggests that various pollutants may not only raise the risk of people developing ALS but also make the disease advance faster.
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a neurodegenerative condition that affects a person's motor neurons — that is, nerve cells that control the movement of muscles.
The disease is progressive and eventually fatal. In 2015, there were more than 16,000 cases of ALS in the United States.
Researchers do not yet know what causes the condition, but scientists have recently been investigating a range of potential risk factors.
For example, one such study suggested that the mercury in fish and seafood can double the risk of developing ALS in people who consume large amounts of fish.
Pesticides have also recently emerged as a potential risk factor. In 2016, Dr. Eva L. Feldman, of the University of Michigan in Ann Arbor, led a study suggesting that exposure to pesticides, such as dichloro-diphenyl-trichloroethane (DDT), methoxychlor, and benzene hexachloride may raise a person's risk of developing ALS in their lifetime.
Now, the same team of researchers has uncovered another class of toxins that may have the same effect on ALS risk: polychlorinated biphenyls, which we also know as PCBs.
What is more, the new research suggests that these chemicals may not only raise the risk of developing ALS, but they also speed up the progression of the disease for people who already have it. PCBs also "correlate with poor survival," in people living with ALS, reports Dr. Feldman.
Studying pollutants and ALS progression
In 2016, Dr. Feldman and her team found increased levels of pesticides in the blood of people living with ALS.
In the new study, the researchers examined the blood levels of various pollutants in 167 people with ALS.
The scientists divided the participants into quartiles, which they based on blood tests and the quantities of pollutants they found in their blood.
The study found that participants in the highest-concentration quartile were likely to survive for 1 year and 11 months, on average.
By contrast, people in the lowest-concentration quartile had an average survival period of 2 years and 6 months.
Dr. Stephen Goutman, a neurologist at Michigan Medicine and the study's first author, comments on the findings, saying, "Our concern is that not only are these factors influencing a person's likelihood to get ALS, but also speeding up disease once they have it."
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