Driving with distraction in Parkinson disease.

OBJECTIVE

To assess the effects of auditory-verbal distraction on driving performance in Parkinson disease (PD).

METHODS

We tested licensed, currently active drivers with mild-to-moderate PD (n = 71) and elderly controls with no neurologic disease (n = 147) on a battery of cognitive, visual, and motor tests. While they drove on a four-lane interstate freeway in an instrumented vehicle, we determined at-fault safety errors and vehicle control measures during a distracter task (Paced Auditory Serial Addition Task [PASAT]) and on an uneventful baseline segment.

RESULTS

Compared with controls, drivers with PD committed more errors during both baseline and distraction, and drove slower with higher speed variability during distraction. Although the average effect of distraction on driving performance compared with baseline was not different between the groups, the drivers with PD showed a more heterogeneous response to distraction (p < 0.001): the error count increased in 28.2% of drivers with PD (vs 15.8% in controls), decreased in 16.9% (vs 3.4%), and remained stable in 54.9% (vs 80.8%). The odds of increase in safety errors due to distraction was higher in the PD group even after adjusting for baseline errors, level of engagement in PASAT, sex, and education (odds ratio [95% CI] = 2.62 [1.19 to 5.74], p = 0.016). Decreased performance on tests of cognitive flexibility, verbal memory, postural control, and increased daytime sleepiness predicted worsening of driving performance due to distraction within the PD group.

CONCLUSION

The quantitative effect of an auditory-verbal distracter task on driving performance was not significantly different between Parkinson disease (PD) and control groups. However, a significantly larger subset of drivers with PD had worsening of their driving safety errors during distraction. Measures of cognition, motor function, and sleepiness predicted effects of distraction on driving performance within the PD group.