Saturday, July 19, 2014

PTSD and Combat Increase Alzheimer’s Risk

When it comes to war, we often worry about our loved ones safety and pray they will come home unharmed. It doesn’t usually happen that way. Some come home with outward injuries, but appearances can be deceptive. Those who appear uninjured often suffer the invisible scars of PTSD (posttraumatic stress disorder) or TBI (traumatic brain injury).

I saw firsthand the effects of PTSD and how life-disrupting it can be. Vietnam changed Jim. I could see some of those changes immediately—sudden loud noises could send him to the ground. While on R&R from Vietnam, the drums from a luau on the beach threw him into instant combat mode. Later, it would be fireworks, gunshots, nightmares, flashbacks, or mental breaks that ripped the scabs off the scars.

Of course, Jim went on to develop dementia, and I couldn’t help but wonder if his PTSD or exposure to Agent Orange could have been an underlying factor. At the time, I found an article linking PTSD to shrinkage of the hippocampus, the brain’s gateway for new memories. VA doctors dismissed the possibility of PTSD playing any part in his memory loss.

Various studies have shown that PTSD is indeed a risk factor for dementia. In addition to PTSD studies are now underway to examine the risk of combat TBI. Brain injury isn’t always caused by a blow to the head; it can also be caused by blasts. In fact, blasts are the cause of most combat traumatic brain injuries.

The Alzheimer’s Neuroimaging Initiative is being used to compare PTSD and TBI as dementia risk factors in Vietnam veterans over age 65. They will be broken down into groups with PTSD only, TBI only, and veterans with both PTSD and TBI. Cohorts should be fully recruited by October 2014. This is the beginnings of a comprehensive study in dementia risk factors in veterans.

Vietnam veterans are being used because of their age because dementia development may take decades. The wars in Iraq, Afghanistan, and acts of terrorism have contributed to more cases of TBI.

Although I’ve focused on TBI in veterans, some of the other causes are sports, vehicle crashes, and the number one cause of TBI: falls. In the United States, 1.4 million suffer TBI each year. The three classifications of TBI are (1) mild—doesn’t knock you out, or less than thirty minutes; (2) moderate—unconscious for more than thirty minutes; and (3) severe—unconscious for more than twenty-four hours.

TBI increases dementia risk. In older adults, moderate TBI more than doubles the risk of Alzheimer’s and severe TBI increases the risk to 4.5 times that of a person who has not had a brain injury. Mild TBI does not increased risk unless it is repeated, such as that caused by contact sports or being exposed to blasts over a period of time.

Adding to the risk factors of TBI is the presence of the apolipoprotein E genotype (APOE). In a study of boxers, all of those who developed severe dementia had at least one copy of APOE-e4.  Another interesting observation with the boxers was that the greatest risk was determined by the number of rounds boxed rather than the number of times a boxer was knocked out. This would indicate that repeated mild TBI was as much of a risk factor as a small number of severe TBIs.

Part of the link between Alzheimer’s disease and TBI is the presence of the hallmarks of Alzheimer’s disease—the proteins beta-amyloid and tau. After a severe brain injury, beta-amyloid will increase within hours. Repeated mild TBI increases the protein tau and sometimes also increases beta-amyloid deposits.

As I worked my way through the statistics, I was struck by a few thoughts. One was that genetic testing on Jim showed that he had one copy of APOE-e4. One copy slightly increased the risk of Alzheimer’s, but not nearly as much as two copies would have. The other thing that struck me was that Jim died at fifty-nine which would have been too young for any study with the age sixty-five threshold. Ironically, if he had not died from dementia, he would have been old enough now. Next month, he would have celebrated his 69th birthday.

Copyright © July 2014 by L.S. Fisher 
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