The ability to maintain a conversation while walking is generally framed as an indication of physical fitness, such that the cognitive skill involved in performing these two distinct tasks simultaneously is ignored or assumed to be trivial. Depending on the difficulty of the tasks, it can take considerable brain resources to properly carry out multiple tasks at the same time. Evidence suggests that the ability to engage in motor (i.e. walking) and cognitive (i.e. having a conversation) tasks at the same time could be a measure of brain health and cognitive aging [1].
Performing two or more types of tasks at the same time is known as dual tasking [2]. These different activities compete for limited brain resources. As the tasks get more challenging, they end up requiring more resources than are available. As a result, the brain has to switch its focus back and forth between the tasks, which can lead to a decline in the performance of the tasks that are not the current focus of attention. For example, walking speeds tend to slow down when someone is focusing on his or her phone.
A study assessing walking quality while doing mathematical calculations found that declines in walking performance during dual tasking became apparent around age 54 to 57 [1]. However, there was considerable variability across individual participants, which may be related to differences in the trajectory of brain aging. Changes in brain structure and functional connectivity that appear to reduce the overall information processing capacity of the brain have been observed starting in the mid-50s [3]. These changes may make the brain less flexible, such that it has more difficulty reliably switching back and forth between tasks, leading to declines in task performance. In the walking study, the ability to maintain walking performance while engaging in a cognitive task was associated with cognitive measures, especially those related to processing and attention [1].
Impairments in walking performance during dual tasking have been seen in the context of several brain-related conditions including Alzheimer’s disease and Parkinson’s disease [4; 5]. Participants with worse dual task performance have been found to be at higher risk for dementia [6], and performance declines in patients with cognitive impairment have been linked to cell loss in brain regions involved in information integration and attention shifting [7]. Meanwhile, some individuals in their 60s and 70s have been found to maintain their dual task performance over time to a level on par with young adults [8]. These ‘superagers’ show evidence of more flexible use of brain resources during times of high demand. This suggests that performance during dual tasking could be a readout of changes taking place in the brain indicating healthy aging or an increased risk for cognitive impairment.
Dual tasking training programs may facilitate brain changes that enhance cognitive flexibility and improve performance. These programs have been widely used in the context of rehabilitation, and many pilot studies have found that they may also offer benefits for patients with cognitive impairment [9; 10], as well as in cognitively healthy older adults [2; 11; 12]. The outcomes in terms of motor or cognitive improvement tend to vary depending on the particular tasks involved in the training program, as benefits may be related to the strengthening of functional connectivity in task-related brain circuits. As a result, tailored dual task training programs involving activities relevant to daily living may be most useful.
These programs have primarily been used to help combat the risk of falling due to reduced walking performance during dual tasking. Various studies have found that dual task training involving walking and balance exercises are effective at improving motor performance. Although benefits to cognitive performance have also been seen, fewer studies have focused on using these training programs to specifically enhance cognition.
Next time you go out for a walk, pay attention to how your stride changes as you start engaging in other activities, such as talking on the phone. See if you notice that you slow down or lose your footing. If so, it may be a sign that your brain is not working at optimal capacity. Engaging in dual task training is one of several steps that you can take that may help boost and maintain brain function with age.
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
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