Vietnam vets' nightmares may unlock hidden link to dementia

SYDNEY — David Hay was almost out of ammunition when a rocket-propelled grenade exploded in the turret of his Centurion tank in the rubber plantation village of Binh Ba, Vietnam, spraying shrapnel into the 21-year-old radio operator's body.

That was 46 years ago, and while the flesh-wounds healed within weeks, Hay had nightmares and bouts of depression for decades.

Now, he and hundreds of other Vietnam veterans are helping doctors try to trace pathways in the brain that may connect the trauma he suffered with the development later in life of one of the world's fastest-growing and most debilitating diseases: Alzheimer's.

For decades, dementia-causing conditions like Alzheimer's were a mystery — illnesses that couldn't be diagnosed for sure except at post-mortem. The development of advanced PET scans, combined with new tracer dyes means that doctors can now follow subtle biological routes in the brain and spinal fluid. That could explain how and why physical and psychological wartime traumas can double the risk of such conditions.

“Vietnam veterans are getting to an age now where we should be picking up changes in those people who are going to develop Alzheimer's,” said Christopher Rowe, director of molecular imaging research at the Austin Hospital in Melbourne, who is leading the Australian arm of the research.

The findings will offer insights into what causes dementia, cases of which are projected to almost double every 20 years. They could shed light on the long-term effects of assaults on the brain — whether sustained in battle, in a car wreck or on the football field, said Michael Weiner, professor of radiology at the University of California, San Francisco School of Medicine, who's leading the study.

“It's long known that there's an association of head injury with Alzheimer's disease,” Weiner said. “But no study has been done with biomarkers to establish the risk.”

About 2 percent of Americans live with disabilities caused by a traumatic brain injury, amounting to $77 billion in costs, according to the U.S. Centers for Disease Control and Prevention. It was associated with about 2.5 million emergency department visits, hospitalizations, or deaths in the U.S. in 2010.

The new study, funded by the U.S. Department of Defense, is looking for early signs of disease in healthy veterans who, like Hay, experienced post-traumatic stress disorder, as well as those who suffered a physical brain injury.

The data is compared with results from veterans who had neither form of injury. About 125 men have been enrolled so far — about a quarter of the number sought in the U.S., Canada and Australia.

The tests are a sign of the growing demand in developed nations for advanced equipment and medical techniques that can diagnose ailments before they become difficult to treat.

The health care business is the second most-profitable of the eight industrial divisions of Munich-based Siemens, one of the world's top three makers of PET, or positron emission tomography, scanners.

The study is also a new avenue for the radioactive liquids made by General Electric, Eli Lilly & Co. and Piramal Enterprises that are injected into a vein and travel through the bloodstream to the brain. These help light up deposits on the scanner of a protein called beta-amyloid that may tip off doctors decades before Alzheimer's dementia ensues.

By understanding the genesis of the disease, doctors hope to be able to prevent it, or at least slow its progression. Results announced in March of Biogen Inc.'s experimental drug for Alzheimer's provide the best evidence so far that the memory-robbing condition is caused by beta-amyloid.

Studies underway with drug candidates made by Eli Lilly and Roche Holding are testing if it's possible to stave off dementia in healthy people with an inherited genetic mutation that causes Alzheimer's and whose PET scans reveal early signs of the disease.

That's encouraging for veterans like Hay.

The number of new cases of Alzheimer's among U.S. veterans is predicted to jump by 423,000 by 2020, Weiner and colleagues estimated in 2013. Of those, 140,000 will be associated with factors specific to the military and lead to as much as $7.8 billion in costs.

Hay was a laboratory technician looking for a change when he volunteered for a two-year stint in the Australian military in 1968.

He ended up as a radio operator in one of four tanks in Binh Ba during one of the fiercest street battles of the war. Hay was loading guns when the RPG exploded, injuring him, the crew commander and gunner.

“I had shrapnel in my face, my eyes, my chest and down my left arm, but that was all superficial,” Hay, now 67, said, recounting an event he resisted sharing with his wife for 20 years and which “still raises hackles on the back of my neck.”

Flashbacks and nightmares haunted him for more than a decade. He suffered depression, moodiness and bursts of anger, and was diagnosed with post-traumatic stress disorder about 25 years ago. The gunner in Hay's crew killed himself after returning to Australia.

“One thing that has always struck me is that, with normal trauma, you get over it in time,” said Hay, who earned a Ph.D. in chemistry after his tour of duty and still works part-time as a scientist with an Australian government research organization.

“People can be in car accidents and they'll recover in time. But PTSD is something that time by itself doesn't heal. There's got to be some part of the brain, deep inside, that's affected permanently and doesn't recover the way the other parts of the body recover.”