Although much research has examined traumatic brain injury (TBI) as a possible risk factor for later-in-life dementia from neurodegenerative diseases such as Alzheimer’s disease (AD), little is known about how TBI influences the rate of age-related cognitive change.
A new study led by Boston University School of Medicine and Boston University School of Public Health (BUSPH) researchers shows that a history of TBI (with loss of consciousness) does not appear to affect the rate of cognitive change over time for participants with normal cognition, or even those with AD dementia.
More than 10 million individuals worldwide are affected annually by TBI, although the true prevalence is likely even greater, given that a majority of TBIs are mild in severity and may not be recognized or reported. TBI is a major public health and socioeconomic concern, resulting in $11.5 billion in direct medical costs and $64.8 billion in indirect costs to the U.S. health system in 2010 alone.
According to the researchers, the relationship between TBI and long-term trajectories remains poorly understood due to limitations of previous studies, including small sample sizes, short follow-up periods, biased samples, high attrition rates, limited or no reports of exposure to repetitive head impacts (such as those received through contact sports), and very brief cognitive test batteries.
In an effort to examine this possible connection, researchers compared performance on cognitive tests over time for 706 participants from the National Alzheimer’s Coordinating Center database. The researchers also examined the possible role of genetics in the relationship between TBI and cognitive decline by studying a gene known to increase risk for AD dementia, the APOE ε4 gene.
The study’s first author, Dr. Yorghos Tripodis, associate director of the data management and biostatistics core of Boston University’s Alzheimer’s Disease Center and associate professor of biostatistics at BUSPH, said the findings should be interpreted cautiously due to the crude and limited assessment of TBI history available.