This study is not the first to uncover similar links, as one study earlier this year showed that 16% percent of veterans who had experienced TBI also developed dementia, compared to only 10% of veterans who had not experienced a brain injury.
However, previous studies were never able to draw direct connections between TBI and dementia due to the limitations of such research, according to Dr. Raquel C. Gardner of the University of California-Sn Francisco and colleagues.
“Even among studies that report a positive association between TBI and dementia, marked variability exists in the magnitude of reported risk,” the researchers add, “which may be due to differences in TBI severity, age of patients, and follow-up period – with some being as short as 2 years – among studies.”
The researchers used information from a health database of ED and inpatient visits in California, which allowed the team to identify 164,661 patients aged 55 years and older who were recently diagnosed with TBI or non-TBI body trauma (NTT) – fractures occurring in areas of the body other than the head or neck.
The team said using NTT patients as control participants improves the study results by preventing the possibility of reverse causality.
Participants in the study were followed-up for an average of 5.7 years and had no signs of dementia at the onset of testing.
Of the 51,799 patients diagnosed with TBI, 8.4% developed dementia, compared with 5.9% of patients diagnosed with NTT. TBI patients also had a shorter duration between trauma and development of dementia, at 3.1 years compared with 3.3 years among NTT patients.
A closer look at the findings showed that moderate to severe TBI at age 55 or older was linked to increased risk of dementia, while mild TBI at age 65 or older also carried similar risks.
“Given the high rates of TBI in the population, primary prevention of TBI, which in this study was overwhelmingly (66.4%) due to falls, is critical,” wrote the researchers.
“The effect of mild TBI sustained in middle age or earlier deserves further study during a longer period of follow-up. In addition, further research is needed to understand the mechanisms of post-TBI dementia to inform secondary preventive strategies.”