No Link Found Between Traumatic Brain Injury and Cognitive Decline.

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 School of Medicine and School of Public Health 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 US 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.

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The study’s first author, Yorghos Tripodis, associate director of the Data Management and Biostatistics Core of the ADC and associate professor of biostatistics, said the findings should be interpreted cautiously due to the crude and limited assessment of TBI history available. The researchers recommended that future studies should collect information on the number of past TBIs (including mild TBIs, as well as exposure to sub-concussive trauma through contact sports and other activities), along with time since TBI, which may play a significant role in cognitive change.