Dual task interference during gait in people with Parkinson disease: effects of motor versus cognitive secondary tasks.

BACKGROUND AND PURPOSE Exacerbation of movement disorders while doing 2 tasks (dual task performance) is a characteristic feature of Parkinson disease (PD). The aim of this investigation was to identify whether the type of secondary task (motor or cognitive) determined the severity of dual task interference. SUBJECTS AND METHODS Footstep patterns for 15 people with PD and 15 comparison subjects without PD were compared when they walked: (1) at a self-selected speed, (2) while simultaneously performing a motor task (coin transference), and (3) while simultaneously performing a cognitive task (digit subtraction). Gait speed, stride length, cadence, and the percentage of the gait cycle in double-limb stance (DS) were examined with a computerized stride analyzer. RESULTS When there was no second task, the mean stride length was less in the group with PD (1.29 m) than in the comparison group (1.51 m), and the mean gait speed was less in the group with PD (71.47 m/min) than in the comparison group (87.29 m/min). The mean cadence was less in the group with PD (110.79 steps/min) than in the comparison group (115.81 steps/min). The percentage of the gait cycle in DS was greater in the group with PD (33.38%) than in the comparison group (31.21%). Both groups reduced their stride length and speed when they had to change from unitask performance to dual task performance and DS increased. For the group with PD, cadence also decreased. For both groups, the type of secondary task had a negligible effect on the performance decrement. DISCUSSION AND CONCLUSION Although the performance of simultaneous motor or cognitive tasks compromised gait in people with PD, the type of secondary task was not a major determinant of the severity of dual task interference.