Effects of Chronic Stress and Acute Stress on Driving Performance

Abstract

The current study examines whether chronic stress due to spousal caregiving, compounded by acute stress, affects driving performance. Ten spousal caregivers completed the 12-item Zarit Burden Interview to assess caregiver burden level. Acute stress was manipulated by having participants complete the Trier Social Stress Test or a control task. Participants then used a driving simulator to complete a car-following (CF) task alone or concurrently with either a divided attention (DA) task, a backward counting (BC) task, or both. They also performed the DA task while driving without car-following requirements. Car-following measures, such as modulus and delay, and vehicle control measures such as standard deviation of lateral position were recorded. Participants also completed the Attention Network Task and the Useful Field of View (UFOV) task. Results indicated that caregiver burden level and acute stress did not degrade driving performance.

Being a spousal caregiver for someone with Alzheimer’s disease or a related dementia (ADRD) is a significant chronic stressor (Chen, 2022). Related to this, people who experience chronic stress are affected more by acute or short-term stressors (Teixeira et al., 2015). Data from recent studies suggest that life stressors may adversely impact driving performance by impairing attentional processes (Cunningham & Regan, 2016). The current study examined whether chronic stress from spousal caregiving for individuals with ADRD, compounded by acute stress, influenced driving performance.

Nine spousal caregivers completed the Zarit Burden Interview (ZBI) to assess caregiver burden (Bédard et al., 2001). To vary acute stress, they completed the Trier Social Stress Test (Kirschbaum et al., 1993) or a control task. Participants completed a car following task alone or concurrently with either a divided attention task, a backward counting task, or both in a STISIM DriveTM simulator. They also performed the divided attention task while driving without car following requirements.

Performance on the car following task was assessed with measures of modulus and delay. STISIM defines modulus as how well the driver matched the lead vehicle’s speed and delay as how long it took the driver to respond to changes in the lead vehicle’s speed (STISIM Drive, n.d.). Vehicular control was assessed with standard deviation of lane position (SDLP).

Participants also completed the Attention Network Task (ANT) and Useful Field of View (UFOV) test to measure attentional capabilities and visual processing speed, respectively (Ball et al., 1988; Fan et al., 2002).

Unexpectedly, results indicated that when caregivers did the control task before driving, they took significantly longer to respond to changes in the lead vehicle’s speed compared to when they did the TSST. There were no significant effects of acute stress or burden level on modulus or SDLP. Participants with moderate levels of burden, as indicated by the ZBI, had significantly lower scores for executive control on the ANT than those with low or high burden levels. There were no effects of stress or burden level on the UFOV test.

In summary, higher levels of acute stress and caregiver burden did not degrade driving performance or performance on the ANT or UFOV test. One possible explanation is that participants may have prioritized performance on the driving task and neglected the divided attention and backward counting tasks. This will be examined with analyses of secondary task performance. Alternatively, effects of chronic stress may not worsen as burden level increases. It is also possible that people with higher burden levels develop coping mechanisms to mitigate effects of chronic stress. A limitation of this study is the lack of a control group with no caregiver burden. Data are currently being collected on age- and gender-matched controls so that a comparison can be made.