Veterans who sustained a mild traumatic brain injury (TBI), even without loss of consciousness (LOC), had a more than twofold higher risk of developing dementia, according to a recent study of more than 350,000 U.S. veterans. Dementia risk was increased among veterans who had sustained moderate-to-severe TBIs, which the investigators say confirms previous studies' findings. But, they note, whether mild TBI increases dementia risk has been controversial, with few studies examining the long-term effects of mild TBI without LOC.
The researchers identified 178,779 patients receiving care from the Veterans Health Administration who were diagnosed with at least one TBI from October 2001 through September 2014 and matched them with controls. The mean age of participants was 49.5 years and more than 90% were men. Dementia was diagnosed in 6.1% of those with a TBI and in 2.6% of those with no TBI. Among those with mild TBI-after adjusting for age, race, other demographic data, and medical and psychiatric diagnoses-adjusted hazard ratios for dementia diagnosis were 2.36 for those without LOC, 2.51 for those with LOC, and 3.19 for those whose LOC status was unknown. The adjusted hazard ratio was 3.77 among veterans with a moderate-to-severe TBI. Among those with dementia, having had a TBI hastened the time to diagnosis of dementia by about a year (a mean of 3.6 years for those with TBI versus 4.8 years for those without).
The authors conclude that these results provide more evidence "suggesting that mild TBI is also associated with increased dementia diagnosis risk," and underscore the need for more research to "determine the mechanisms underlying the association observed between TBI and dementia, including mild TBI without LOC, so that effective treatment and prevention strategies can be developed."
Their findings have implications beyond the veteran population: in 2013, there were about 2.8 million TBIs in the United States, of which about 80% were mild, according to the authors.-Elizabeth Mechcatie, MA, BSN
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