A mild traumatic brain injury (TBI), including a concussion, can increase a person’s risk of developing Parkinson’s disease by more than 50 percent, a study conducted in U.S. military veterans reports.
The study, “Mild TBI and risk of Parkinson disease: A Chronic Effects of Neurotrauma Consortium Study,” appeared in the journal Neurology.
Studies have shown a strong link between moderate to severe TBI and a Parkinson’s diagnosis. But evidence as to how a mild TBI might weigh on disease development is inconclusive.
Researchers with the San Francisco Veterans Affairs Medical Center and the University of California, San Francisco aimed to address this gap in a study that relied on records from three Veterans Health Administration databases.
“Our research looked a very large population of U.S. veterans who had experienced either mild, moderate or severe traumatic brain injury in an effort to find an answer to whether [mild TBI] can put someone at risk,” Kristine Yaffe, MD, the study’s senior author, said in a press release.
Moderate to severe TBI was defined as a loss of consciousness for more than 30 minutes, or a change in consciousness or amnesia lasting more than 24 hours. Mild TBI was classified as an unconscious state lasting up to 30 minutes, or a change in consciousness or amnesia of 24 hours or less.
None of the 325,870 veterans identified for this study — 47.9 years old, on average — had a Parkinson’s or dementia diagnosis at its start. But about half had been treated for either a mild, moderate, or severe traumatic brain injury.
In total, 1,462 of these veterans were diagnosed with Parkinson’s during the study, in follow-up examinations of between one and 12 years.
Analysis revealed that most — 949 of the 1,462 — had a TBI prior to the Parkinson’s diagnosis, while the remaining 513 did not. Specifically, 360 out of 76,297 veterans diagnosed with a mild TBI developed Parkinson’s (0.47%), as did 543 out of 72,592 with a history of moderate to severe TBI (0.75%).
Subsequent analysis — after adjusting for sex, age, race, education, and overall health — found that traumatic brain injury of any kind increased the risk of Parkinson’s by 71% in this group of veterans. Those with moderate to severe injuries were at greatest risk — an 83% increase — while veterans with mild TBI had a 56% increased risk.
Parkinson’s was also diagnosed in TBI patients, on average, two years earlier than in those without such brain injuries.
“This study highlights the importance of concussion prevention, long-term follow-up of those with concussion, and the need for future studies to investigate if there are other risk factors for Parkinson’s disease that can be modified after someone has a concussion,” said Raquel C. Gardner, MD, the study’s first author.
“Because the majority of TBIs sustained by military veterans occur during civilian life either before or after military service, the results of this study may additionally have important implications for civilian and athlete populations,” she added.
The researchers also noted as a study limitation that mild cases of TBI may be underreported in military personnel serving in combat.