Concussions, TBI Linked to Increased Dementia Risks

Deborah Barnes, PhD, MPH

A new study has found that concussions can increase the likelihood of dementia in a patient by two-fold.

Researchers from the University of California San Francisco (UCSF) Weill Institute for Neurosciences and the San Francisco Veterans Affairs Health Care System conducted analysis on more than 350,000 veterans to find the risk of complications in those who suffered from concussions.

They found that those who had experienced a concussion without loss of consciousness had a 2.36-times greater risk for dementia, after adjustments for age, sex, race, education, and other health conditions. For those who suffered concussions with loss of consciousness, risk of dementia was 2.51 times greater. Those with moderate-to-severe traumatic brain injury (TBI) had a 3.77-times greater risk.

The analysis was pulled from 2 databases: one with veterans of various generations who had suffered TBIs ranging from concussion to mild TBI in either their military career or civilian life; and another list of veterans who served in Iraq and Afghanistan. The latter list’s veterans were more likely to suffer TBI in combat zones.

The 357,558 study participants (mean age 49) were tracked for an average of 4.2 years. The patients were most frequently male (91%) and white (72%). Researchers defined concussions among Iraq and Afghanistan veterans as mild TBI that resulted in alteration of consciousness and amnesia for up to 1 day, based on medical evaluation. Concussion was defined in other veterans though comprehensive diagnostic codes in electronic health records.

First author Deborah Barnes, PhD, MPH, professor in the UCSF Departments of Psychiatry, and Epidemiology and Biostatistics, said the finding were similar across both lists — meaning concussions suffered by common civilians induce as much risk of dementia as combat-area TBIs.

The study results contribute to a growing collection of research that links concussions and TBI to multiple neurodegenerative or psychiatric conditions — including previous work by the UCSF team itself. Just last month, they presented data indicating a link between concussions and Parkinson’s disease.

But the results also show an unmet need in reducing TBI likelihood, Barnes said. Though their study did not directly examine the cumulative effect of repeated concussions in patients, the evidence is beginning to show itself.

“In older adults, exercise and multifactorial interventions may limit the risks of falls, which are a leading cause of head injury,” Barnes said. “For those who experience a concussion, get medical attention, allow time to heal and try to avoid repeat concussions.”

Kristine Yaffe, MD, professor in the UCSF Departments of Neurology, Psychiatry, and Epidemiology and Biostatistics, said trauma likely hastens the development of neurodegenerative diseases. Some evidential mechanisms between the 2 events may someday better explain the link.

“One theory is that brain injury induces or accelerates the accumulation of abnormal proteins that lead to neuronal death associated with conditions like Alzheimer’s disease,” Yaffe said. “It’s also possible that trauma leaves the brain more vulnerable to other injuries or aging processes, but we need more work in this area.”

The research team received funding from the US Army Medical Research and Material Command, as well as from the US Department of Veteran Affairs.

The study, "Association of Mild Traumatic Brain Injury With and Without Loss of Consciousness With Dementia in US Military Veterans," was published online in JAMA Neurology Monday morning.