Using brain scans and exercise stress tests, researchers have identified two biologically distinct subgroups of veterans suffering from so-called Gulf War illness.
Their bodies reacted differently to physical exertion, and their brains had atrophied in different regions. None of the patterns were seen in a control group of healthy subjects.
The findings, published online Friday in the journal PLOS One, are part of a growing body of work that the authors said could eventually lead to biological markers for the mysterious condition, which is still defined defined by its hodgepodge of symptoms.
“That’s the hope,” said Georgetown University researcher Rakib Rayhan, lead author of the study.
Still, the importance of the differences his team identified is far from clear, said Dr. Beatrice Golomb, an expert on Gulf War illness at UC San Diego who was not involved in the research.
There are many ways to parse any population of patients with a condition that is so variable and diverse, she said. After the 1991 Persian Gulf War, veterans began complaining of a wide range of problems, including pain, fatigue, headaches and cognitive impairment. The symptoms ranged from mild to debilitating.
Up to 30% of the 700,000 troops who served in the war are thought to be affected.
Though exposure to nerve agents, pesticides and smoke from burning oil wells have all been deemed possible culprits, no definitive cause has been identified.
“It was a very toxic environment we were around,” said 54-year-old Angela McLamb, who developed symptoms of Gulf War illness in 1991 while she was on a U.S. base in Saudi Arabia working as an air traffic controller.
She has suffered ever since from problems ranging from severe fatigue to speech and memory difficulties, she said, and can no longer work. “We used to be in excellent shape,” she said. “But our bodies have been destroyed from within.”
She was one of 28 veterans with the condition participating in the study.
The Georgetown team set out to look at the structure and function of their brains.
Each subject received two brain scans while undergoing cognitive testing — one at rest and one after an exercise session on a stationary bicycle. Physical exertion can cause extreme malaise in veterans suffering from the condition, and the researchers wanted to see how it affected their brains.
The hourlong scans, known as functional MRIs, allow scientists to see the structure of the brain and which parts are being activated. The veterans also underwent various physiological tests.
To the surprise of the researchers, two groups of veterans emerged in the analysis.
In 18 of the veterans, levels of pain were elevated after exercise. Their scans showed a loss of brain matter in the regions associated with pain regulation.
In the other 10 veterans, exercise triggered a condition in which moving from lying down to standing causes the heart to race. They had atrophy in the brain stem, which controls heart rate and blood pressure.
The two groups also had distinct patterns of brain activity during cognitive testing.
McLamb said the discovery of biological markers for Gulf War illness would help eliminate a popular but increasingly discredited belief that the condition is psychological and stems from stress.
“I never thought I would be happy to say I have brain damage,” she said. “But I am. Because I deal with this on a daily basis.”
Twitter: @alanzarembo