Dementia Risk Still Evident 30 Years After TBI

Although the risk of dementia may decrease over time among individuals with traumatic brain injury (TBI), this risk is still present 30 years after the trauma, results of a new study showed.

For their study, the researchers identified 3,329,360 individuals in Sweden aged at least 50 years on December 31, 2005, and recorded diagnoses of dementia and TBI from 1964 to December 31, 2012. Mean follow-up lasted 15.3 years.
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One cohort was composed of 164,334 individuals with a diagnosis of TBI, who were matched with 2 controls each. The second cohort included 136,233 individuals diagnosed with dementia over the course of follow-up, who were also matched with 2 controls each. The third cohort included 46,970 full sibling pairs with discordant TBI status.

Dementia had been diagnosed in 21,963 individuals in the first cohort over the course of follow-up (adjusted odds ratio [OR] 1.81). Of these patients, 6.3% had TBI, while 3.6% did not. The researchers observed that the association between TBI and dementia risk was strongest within the first year following TBI (OR 3.52) but was still significant even 30 years or more after the trauma (OR 1.25).

Ultimately, the association of TBI with dementia was higher in patients with more severe TBI (OR 2.06) and multiple TBIs (OR 2.81) vs those with a single mild TBI (OR 1.63). Similar results were observed in the nested case-control cohort.

The researchers also noted that TBI was associated with a higher risk for dementia in sibling pairs with discordant TBI status (OR 1.89).

“The risk of dementia diagnosis decreased over time after TBI, but it was still evident >30 years after the trauma,” the researchers concluded. “The association was stronger for more severe TBI and multiple TBIs, and it persisted after adjustment for familial factors.”

—Christina Vogt

Reference:

Nordström A, Nordström P. Traumatic brain injury and the risk of dementia diagnosis: A nationwide cohort study [Published online January 30, 2018]. PLOS Med. https://doi.org/10.1371/journal.pmed.1002496.