(CNN) There's something about military life that is putting our nation's vets in harm's way, and it's not the usual suspects.

It's not a military action or terrorist threat, but a horrifying disease that weakens muscles to the point of paralysis, ultimately trapping people inside their bodies, completely aware, yet unable to move or even breathe without help.

It's Lou Gehrig's disease, also called amyotrophic lateral sclerosis, or ALS, and studies show that if you've served in the military -- any branch, any war, or even if you served in a time of peace -- you have a much higher risk of dying from it than if you were not in the military. And no one seems to know why.

David Masters was serving in Kuwait when his symptoms first started.

"I was weight training, working out in the gym, and my right arm did not want to cooperate, did not want to keep up," explained Masters. "I was 28, just turning 29 years old, and I thought it was a pinched nerve, but it kept getting weaker and weaker."

In the best shape of his life, Masters had his sights set on a bodybuilding career. After his temporary duty assignment in Kuwait ended, the staff sergeant returned to the States, but Air Force doctors couldn't figure out what was wrong.

'See a neurologist right now'

"I was frustrated, my bodybuilding career that I was trying to get off the ground was over, and I just gave up. Then my fingers started to act up, getting numb. By the time I went to a doctor for that in early winter 2006, the doctor said, 'You need to see a neurologist right now.'"

He was diagnosed with progressive muscular atrophy , which studies show can turn into Lou Gehrig's disease. Sure enough, by March of 2010, Masters was diagnosed with full-blown ALS. But most cases don't have such a slow progression.

Carlo Russo, years before his ALS diagnosis, smiles with wife Karen.

Karen Russo's husband, Carlo, is another case. A Marine, he served for four years in Hawaii as a photographer and journalist during the Vietnam era, but never saw combat. A chef by trade, he began developing symptoms much later in life, at age 55.

"He had weakness in his right hand and arm, he kept dropping things," said Karen. "Then his right leg weakened and he fell a couple of times, which was really out of character. The doctors did an EMG (needle electromyography); it's a test that's pretty definitive for ALS. He was diagnosed the same day. That was in August. By Thanksgiving he was in a wheelchair."

Tim Hoyt also never saw combat. He was drafted into the Vietnam War at age 19, but spent his two-year stint as a radio-electronic specialist stationed in Germany.

Chemistry professor Tim Hoyt gives a scientific demonstration as "the Wiz."

He was diagnosed with ALS in March 2013, at the age of 65. It wasn't long until he had to leave his job as a chemistry professor at the University of Puget Sound, where he was known as "the Wiz" for his looks and love of scientific magic shows

"It was my arm that went first," said Hoyt. "My right arm, right hand got very weak, I couldn't hold the chalk to the blackboard. It's now progressed to (my) left arm. Both arms and hands are useless. I'm still walking, though I'm weak."

Even now, not much is known

Lou Gehrig's disease was discovered in 1869, almost 150 years ago. But according to the ALS Association , the prognosis for anyone diagnosed with the disease is the same as it was then: "death in an average of two to five years."

Between 5% and 10% of ALS cases are hereditary; the rest occur for unknown reasons. Smoking, being male, white and older than 60 are the most closely associated risk factors for the general population. Beyond that, studies are contradictory or unclear, especially when it comes to the military connection. Basically what we know is that veterans have a 60% higher risk of getting ALS than the general population.

"We don't know what about service could lead to increased risk of the disease in veterans," said Patrick Wildman, vice president of public policy for the ALS Association. "It could be a variety of factors from head trauma and excessive physical activity to exposures. It also could be a combination of a genetic predisposition with an environmental trigger."

The Mayo Clinic guesses that reasons for the connection "may include exposure to certain metals or chemicals, traumatic injuries, viral infections and intense exertion" but says that "exactly what about military service may trigger the development of ALS is uncertain."

Impact of the Ice Bucket Challenge

Thanks in part to the ALS Ice Bucket Challenge, ALS research is on fire, said Harvard's Dr. Merit Cudkowicz

"More funding is available; lots of new clinical trials and hope for people living with ALS today. Still, we need a Manhattan-type project on ALS -- all hands on deck to figure this out and make an impact on the illness. For rare disorders, the key is to share data and collaborate."

The Department of Veterans Affairs considers ALS a full service-related disease. That's a blessing for veterans and their families, who can't imagine how they would cope with the expenses.

Tim Hoyt, a Vietnam-era vet, was diagnosed with ALS at the age of 65.

"The VA's been right up there with disability pay," said Hoyt. "They pay for the caregiving I get in the mornings. I've got a wheelchair from them, a wheelchair ramp; those range from ($20,000) to $50,000. I have a wheelchair van (and) a special housing grant from the VA that allowed me to get an elevator so I can stay in my home and live in all of it, not just one floor."

Masters agrees, but added this advice to veterans who may think they are seeing symptoms: "Documentation is key when it comes to military. Making sure your medical records are accurate should be a personal responsibility -- you cannot rely on the military or anyone else. It may have big-time consequences if you don't."

"For the newly diagnosed," Masters added, "they need to reach out to the VA organizations such as Paralyzed Veterans of America or Disabled American Veterans , some organization that will represent them to the VA so they will get the maximum benefits they deserve."

Worst disease she can imagine

Carlo Russo lived for 10 years with the disease, passing away just last month. For Karen, a registered nurse, ALS is the worst disease she can imagine, and no amount of financial support can help.

"Carlo was alert, oriented, but he couldn't move. He could only blink his eyes for many years. Caregiving was intense. It's 24/7. There were times I didn't have a night nurse and had to be there all day and all night, and sleep with one eye open next to him."

Even more exhausting was when the ventilation machine that kept him alive would fail.

Carlo Russo is surrounded by his children and grandchildren.

"There were bells and whistles on the vent that would go off, say, if he coughed." said Karen. "The vent would come apart for no reason. That was an emergency, you had to figure out which part was malfunctioning and fix it -- fast. It was very frightening. I don't think I had a day that went by that I didn't have the feeling 'I don't know if I can fix this,' and it's very scary if you're by yourself."

Yet, despite it all, Karen is thankful for the 10 years she got with the love of her life, years more than many with ALS manage to get. And she never heard her husband complain.

"Carlo was extremely brave," said Karen. "He never once said 'Why me?' or 'Why do I have this?' or 'I wish I'd never been in the service.' He never went there. I would say my husband enjoyed the 10 years that he had because of the support of his family and friends. We included him in every way and took him along as much as we could. So hang in there. Where's there's love there's a way."