Daily driving behavior is ultimate measure of cognitive functioning requiring multiple cognitive domains working synergistically to complete this complex instrumental activity of daily living. As the world’s population continues to grow and age older, motor vehicle crashes become more frequent. Cognitive and brain reserve are developing constructs that are frequently assessed in aging research. Cognitive reserve preserves functioning in the face of greater loss of brain structure as experienced during cognitive impairment or dementia. This study determined whether cognitive reserve and brain reserve predict changes in adverse driving behaviors in cognitively normal older adults.

Cognitively normal participants (Clinical Dementia Rating 0) were enrolled from longitudinal studies at the Knight Alzheimer’s Disease Research Center at Washington University. Participants (n=186) were ≥ 65 years of age, required to have Magnetic Resonance Imaging (MRI) data, neuropsychological testing data, as well as one full year of naturalistic driving data prior to the beginning of COVID-19 lockdown in the United States (March 2020). Naturalistic driving behavior data was collected via the Driving Real World In-vehicle Evaluation System (DRIVES). DRIVES variables included idle time, over speeding, aggression, number of trips, including those at day and night. MRI was performed on 3T Tesla using a research imaging protocol based upon ADNI that includes a high-resolution T1 MPRAGE for assessment of brain structures to produce normalized whole brain volume (WBV) and hippocampal volume (HV). WBV and HV were each assessed using tertiles comparing the top 66% with the bottom 33% where the bottom represented increased atrophy. The Word Reading subtest of the Wide Range Achievement Test 4 (WRAT 4) was utilized as a proxy for cognitive reserve. WRAT 4 scores were compared with the top 66% and the bottom 33% where the bottom were poor performers. Linear-mixed-effect models adjusted for age, education, and sex.

Participants on average were older (73.7±4.9), college educated (16.6±2.2), and similar sex distribution (males=100, females=86). Analyses showed statistically significant differences in slopes where participants with increased hippocampal and whole brain atrophy were less likely to overspeed (p=0.0035; p=0.0003), drive aggressively (p=0.0016; p<0.0001), and drive during the daytime (p<0.0001; p<0.0001). However, they were more likely to spend more time idling (p=0.0005; p<0.0001) and drive during the nighttime (p=0.003; p=0.0002). Similar findings occurred with the WRAT 4 where participants with lower scores were less likely to overspeed (p=0.0035), drive aggressively (p=0.0024), hard brake (p=0.0180), and drive during the daytime (p<0.0001) while they were more likely to also spend more time idling (p=0.0012) and drive during the nighttime (p=0.0004).

Numerous changes in driving behaviors over time were predicted by increased hippocampal and whole brain atrophy as well as lower cognitive reserve scores proxied by the WRAT 4. These changes show that those with lower brain and cognitive reserve are more likely to restrict their driving behavior and adapt their daily behaviors as they age. These results suggest older adults with lower brain and cognitive reserve are more likely to avoid highways where speeding and aggressive maneuvers are more frequent.