Neuroimaging Correlates of Traumatic Brain Injury in an Older Community-Dwelling Population: The Atherosclerosis Risk in Communities Study.

BACKGROUND AND OBJECTIVES

Neuroimaging correlates of remote traumatic brain injury (TBI) are not well understood. Our objective was to examine associations of TBI with brain MRI markers of degeneration and vascular disease.

METHODS

We performed a cross-sectional analysis using data from a subset of participants who underwent a 3T brain MRI during the fifth Atherosclerosis Risk in Communities Study visit in 2011-2013. Prior TBI and age at first TBI (<18 years, 18-65 years, >65 years) was defined using self-report and International Classification of Diseases, Ninth Edition code data. We examined the following brain MRI metrics: presence of infarcts and microhemorrhages, white matter hyperintensity (WMH) volume, and the distribution of the number of regions of interest (ROIs) below a -score cut-point of -1.5 for volumetrics, cortical thickness, and fractional anisotropy (FA) and above +1.5 for mean diffusivity (MD).

RESULTS

A total of 1,642 participants were included (mean age 76.8 ± 5.32 years, 61.0% female, 28.3% self-reported Black race, and 25.5% with a history of TBI [median time between first TBI and MRI: 38.2 years]). There was no evidence of differences in vascular imaging findings by overall TBI status, but individuals who sustained their first TBI at age <18 years had higher WMH volume (adjusted β = 0.22 mm, 95% CI 0.00-0.43) and individuals who sustained their first TBI at age >65 years were more likely to have subcortical microhemorrhages (adjusted OR 1.69, 95% CI 1.03-2.75) compared with individuals without TBI. Compared with individuals without TBI, individuals with a history of TBI had a greater number of ROIs beyond the -score cut-point for all metrics (smaller volumes, lower cortical thickness, lower FA, and higher MD). These findings were consistent among participants with first TBI sustained at age >65 years old, whereas participants with first TBI sustained at age <18 years old had a greater number of regions beyond the -score cut-point only for FA and MD.

DISCUSSION

In this community-dwelling cohort of older adults, TBI was associated with smaller brain volumes, lower cortical thickness, lower FA, and higher MD. Further work is needed in the chronic postinjury period to elucidate the mechanisms underlying the observed structural changes after TBI.