It has been suggested in the past that the ability to walk while concurrently engaging in a second task deteriorates in old age, and that this deficit is related to the high incidence of falls in the elderly. However, previous studies provided inconsistent findings about the existence of such an age-related dual-task deficit (ARD). In an effort to explain this inconsistency, we explored whether ARD while walking emerges for some, but not for other types of task.
Healthy young and elderly subjects were tested under five different combinations of a walking and a non-walking task. The results were analysed jointly with those of a previous study from our lab, such that a total of 13 task combinations were evaluated. For each task combination and subject, we calculated the mean dual-task costs across both constituent tasks, and quantified ARD as the difference between those costs in elderly and in young subjects.
An analysis of covariance yielded no significant effects of obstacle presence and overall task difficulty on ARD, but a highly significant effect of visual demand: non-walking tasks which required ongoing visual observation led to ARD of more than 8%, while those without such requirements led to near-zero ARD. We therefore concluded that the visual demand of the non-walking task is critical for the emergence of ARD while walking.