By Gila Reckess
February 9, 2001
School of Medicine research- ers have identified the first clue that welding might trigger early onset of Parkinson's disease.
A research team led by neurologist Brad A. Racette, M.D., found that 15 professional welders developed typical clinical and neurological signs of the disease an average of 15 years earlier than the general population. The study is featured in the January issue of the journal Neurology with an accompanying editorial.
"This research doesn't prove that welding causes Parkinson's disease," said Racette, assistant professor of neurology. "But it's suspicious that the majority of these patients had a much younger age of onset. Our theory is that we have identified a group of people who probably would have developed the disease eventually, but something in the welding environment caused them to develop symptoms earlier."
Parkinson's disease is a progressive movement disorder that affects more than 1 million Americans. It is characterized by slowness of movement and tremors that affect one side of the body more than the other.
Scientists have therefore hypothesized that environmental factors are largely responsible. However, no such factors have been identified.
One clue, though, is that manganese miners are susceptible to a condition called manganism because they inhale large amounts of the mineral. The disease is classified as a Parkinson syndrome because it bears a resemblance to Parkinson's disease. But both the symptoms and brain pathology are significantly different.
Welding fumes also contain high levels of manganese. But when a young welder walked into Racette's office and said he was suffering from manganism, Racette knew something was fishy.
"Manganism is a very different disease," Racette said. "To me, this patient clearly looked as if he had Parkinson's."
He soon discovered lore that welding might lead to Parkinson's; material data safety sheets even list the disease as a possible hazard. But there is little scientific evidence to back up the idea.
Racette and colleagues therefore set out to determine whether welding is an environmental contributor to Parkinson's. They identified 15 professional welders among patients in the medical school's Movement Disorders Center. Then they compared the welders' medical history and clinical symptoms with those of control patients with Parkinson's.
They found no clinical differences between the welders and typical patients with Parkinson's. The two groups had the same severity and frequency of symptoms and responded similarly to levodopa, a drug used to treat Parkinson's.
The only statistically significant difference was average age of onset: 45 for the welders, or 15 years younger than for the control group.
Racette and his colleagues also imaged the brains of two of the welding patients and 13 control patients. People with Parkinson's typically have lower levels of a neurotransmitter called dopamine in certain regions of their brain.
Using a technique called fluorodopa positron emission tomography (FDOPA PET), researchers determined how much dopamine the brain used. With that information, they assessed the extent of Parkinson-like deterioration. The FDOPA PET scans revealed no significant difference between the welding and control groups. Therefore, the welders appeared to have typical Parkinson's disease.
"These results are really exciting because we may soon be able to identify the first environmental cause of Parkinson's," Racette said. "Our first goal is to show that welding truly does cause this disease. Then we can figure out which aspect of welding is responsible."
This information, Racette argues, will help determine whether welders should take precautionary measures and also will help researchers begin to unlock the underlying cause of this debilitating disorder.
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