Impaired updating ability in drivers with Parkinson's disease.

OBJECTIVE Driving activity requires major involvement of executive functions. The main objective of our study was to determine whether mental flexibility and the updating of information in working memory are affected in drivers with mild to moderate Parkinson's disease (PD). METHODS The study included 25 patients, aged 58-76, with mild to moderate PD and 25 healthy controls matched for age, sex and education, with an average mileage of over 3000 km/year. Neuropsychological tests were conducted to assess global cognitive abilities, to evaluate updating (via the n-back task), flexibility (via the plus-minus task) and information-processing speed (via the Stroop test). Three different scenarios were developed on a driving simulator. Participants were asked to recall road signs (updating task), indicate the shape or colour of road signs according to road side (flexibility task) and to brake at the same time as the car ahead (information-processing speed task) while driving. RESULTS An updating impairment was found in PD patients in the n-back and simulator tasks; patients recalled significantly fewer road signs. No notable differences were observed between groups in the plus-minus task or in the simulator task evaluating flexibility. There was no significant difference between patients and controls in information-processing speed tasks. Regression analysis showed that the Trail-Making test (B-A) accounted for 40.7% of the variation in PD drivers' simulator task updating score. CONCLUSION The updating function is clearly impaired in drivers with mild to moderate PD, while mental flexibility remains unaffected. This study demonstrates the interest of using the Trail Making Test and simulator tasks to assess PD drivers.