Concurrent listening impairs compensatory postural control mechanisms in middle and late adulthood.

Multitasking involving sensorimotor functions has been shown to affect older more than young adults but little is known about whether related challenges already emerge in middle adulthood. Here we compare 21 younger (18-30 years of age), 23 middle-aged (45-65 years of age) and 19 older participants (66-81 years of age) who listened to and memorized spoken words while they tried to maintain a stable posture on a force platform. The number of words in the listening task was adjusted to individual single-task levels and cognitive control demands were manipulated by presenting words from either the same or switching target speakers. Postural control demands were varied by manipulating proprioceptive reliability (stable stance or sway-referencing). Young adults' listening and postural control remained unaffected by concurrent performances. During multitasking middle-aged and older adults maintained single-task levels in listening, however, their postural stability declined significantly. Stabilogram diffusion analysis identified efficiency and timing of long-term corrective mechanisms as the key processes affected by multitasking. We argue that middle-aged adults can maintain young-adult levels of postural stability under ideal conditions by cognitive compensation for sensorimotor decline, a process breaking down during multitasking. Our findings illustrate that multitasking in ecologically relevant listening and postural control settings presents a significant challenge as early as middle adulthood.