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Do veterans with a history of concussion face higher risk for Parkinson’s? What the research shows

In a recent commentary piece, The Defense Post called attention to an issue of concern among the veterans’ community—namely, the potentially severe health risks posed by an all-too-common and misleadingly-named condition: mild traumatic brain injury (mTBI). mTBI (more commonly known as concussion) afflicts members of the military at an alarmingly high rate. All told, over 350,000 non-penetrating mTBI injuries were reported among servicepersons between 2000 and 2018. In all likelihood, the real numbers are even higher. As Michael Wyand, author of the Defense Post article asserts, “it is a moral imperative for us to address this epidemic with immediacy for those who served, are currently serving, and will serve in the future.”

Use of the term “mild” to describe mTBI is somewhat of a misnomer

While not life-threatening in the moment, concussions are hardly innocuous health incidents. As public awareness continues to grow around conditions that involve seemingly less-acute head traumas, such as Chronic Traumatic Encephalopathy (CTE), the scientific community is beginning to better understand the long-term side effects of sustaining an mTBI (or multiple mTBIs) and its collective impact on the health outcomes of veterans.

That concussions can impair brain and overall health in both the near- and long terms, of course, is not news for the thousands of current and former servicepersons who have sustained such an injury. “Concussions are more than a passing rattling of the head for some soldiers,” Wyand observes. “Many of our veterans from Operation Freedom, Operation Iraqi Freedom, and Operation New Dawn just can’t shake off mild traumatic brain injury.” Yet veterans with a history of concussion might have experienced frustration due to the lack of available answers for why mTBIs produce lasting side effects, which can range from brain fog and persistent headaches to mood instability. 

Fortunately, a recent study cited by Wyand might offer some clues. That research, which centered on veterans, raised alarm bells by revealing that a history of mTBI and early-stage Parkinson’s Disease (PD) produce a similar pattern of premature cognitive impairment. PD is a progressive neurodegenerative disorder that often results in tremors, limb stiffness, and challenges with coordination. 

This post will discuss the key findings of the study, which was conducted at the University of North Texas Health Science Center between 2017 and 2020 and published in the peer-reviewed journal PLOS One last November. 

New research shows a link between mTBI and Parkinson’s in veterans

The cross-sectional, matched case-control study sought to assess whether a common cognitive phenotype exists among mTBI and Parkinson’s Disease (PD). Such a finding would substantiate previous research indicating that mTBI might trigger the eventual onset of PD, including a 2018 study which found that veterans who sustained an mTBI faced a 56 percent increased risk of developing PD within 12 years. 

To do so, researchers compared the cognitive functioning of young veterans with a positive history of mTBI against that of age- and IQ-matched veterans without mTBI, age- and IQ-matched non-veteran controls without mTBI, and IQ-matched elderly participants with early-stage PD. 123 participants underwent testing in a medical laboratory to probe whether the group of young, mTBI-positive veterans demonstrated similar subclinical symptoms of premature cognitive decline as the early-stage PD group. 

Major takeaways of the research

The young, mTBI-positive veteran group exhibited signs of early cognitive decline similar to those found in the early-stage PD group across certain, highly specific areas, including cognitive flexibility; attention; processing speed; and inhibitory control. Within those cognitive domains, the mTBI-positive veterans presented as three decades older than their actual ages. 

Importantly, the cognitive performance of the mTBI-positive veterans and early-stage PD groups also appeared unaffected in several common areas, as compared to the age- and IQ-matched controls. Those unimpacted domains included phonemic verbal fluency, visuospatial memory, and working memory capacity.

Such an overlap between the areas in which cognitive performance appeared to be affected or spared portends a link between a history of mTBI and PD. 

What’s needed: more research, more advocacy for those with mTBI

Given that thousands of servicepersons sustain mTBIs every year, these findings have implications for the veterans’ community as a whole. Indeed, this research demonstrates that it is vital for us all to remember that concussions are not mild injuries. As this study shows, veterans with a history of mTBI exhibited a premature cognitive decline in domains consistent with early-stage PD, suggesting that mTBI might serve as a precursor to PD or other neurodegenerative conditions. 

Because clinical symptoms of cognitive decline often do not appear for 8 or more years after sustaining an mTBI, or 7 to 13 years before the onset of motor impairment in PD, identifying these subclinical areas of premature cognitive decline in specific areas, such as cognitive flexibility, is critical for early detection. Caught at an earlier stage, subclinical cognitive decline can be targeted through various interventions that work to prevent the progression of cognitive impairment, neurodegeneration, and dementia. 

Just as important, it is crucial that the veterans’ community, clinicians and researchers, and the federal government come together to demand and fund continued research into treatments for brain injuries. Through tandem education and advocacy efforts, it is possible to realize the urgent goal of safeguarding and treating the brain health of veterans. 

Read the Research

Nejtek VA, James RN, Salvatore MF, Alphonso HM, Boehm GW (2021). Premature cognitive decline in specific domains found in young veterans with mTBI coincides with elder normative scores and advanced-age subjects with early-stage Parkinson’s disease. PLoS ONE 16(11): e0258851. 

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