People with Lou Gehrig's disease, or ALS, are more likely to have been exposed to toxic pesticides or to have served in the military than similar people without the condition, according to a new study.
ALS, or amyotrophic lateral sclerosis, is a degenerative disease in which nerve cells break down over time. ALS affects fewer than 20,000 people in the U.S. each year, according to the Mayo Clinic.
The disease is progressive, eventually affecting the ability to chew, swallow, speak and breathe. In 2014, the ALS "Ice Bucket Challenge" went viral on the internet and helped raise $115 million for research toward a cure.
"The environmental risk of ALS has been a concern for many years," said senior author Dr. Eva L. Feldman of the Alfred Taubman Medical Research Institute at the University of Michigan in Ann Arbor.
Earlier studies have linked environmental exposures - including exposure to pesticides - to the likelihood of having ALS, Feldman told Reuters Health by email.
The new study may help shed light on the mechanisms of ALS, she said.
Participants completed questionnaires on their exposure to toxins at work and provided blood samples. Their blood was tested for environmental pollutants including those found in pesticides and flame retardants as well as polychlorinated biphenyls (PCBs), banned chemicals that still contaminate some rivers and other sites.
Using age, sex, educational level, smoking status and occupational risk factors as well as blood test results, the researchers compared 101 adults with diagnosed or probable ALS and 110 adults without ALS, on average around age 60.
Those with ALS were more likely to report pesticide exposure or to have ever served in the military than those without the disease, the researchers reported in JAMA Neurology.
"The cause of ALS remains complex and we believe that multiple factors, including environmental exposures, play a role," said coauthor Dr. Stephen Goutman, director of the ALS clinic at the University of Michigan. "A leading hypothesis is that underlying genetic susceptibility factors combined with environmental risk factors lead to toxicity that triggers the disease."
Chemicals in pesticides may affect the way nerves function, Goutman told Reuters Health by email.
It's too soon to know how much chemical exposure actually affects ALS risk, or why military exposure would be related, Feldman said.
Everyone in the study had some of the environmental pollutants in their blood, she said. But those with ALS had "clearly greater exposure."
"I am concerned about these associations and we, as a research community, need to better understand what they mean and how they relate to ALS onset and progression," Goutman said.
In the meantime, he said, "we encourage individuals to focus on helping to keep our environment pollutant free in any way, small or large, that they can."