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Submitted by Darlene Reid, BMR, PhD
Background – Does multitasking take more brain-power and lead to more mistakes?
Multitasking, such as walking across the street while looking at a cell phone, often results in doing one or both things poorly. People with cognitive impairment have more limitations when multitasking because they do not have the “brain-power” to do more than one activity with complete accuracy. For decades, people with chronic obstructive pulmonary disease (COPD) have been known to have mental challenges with memory and attention. The reported prevalence of cognitive impairment in people with COPD ranges between 36 to 57%.1-3 Research has focused on how cognitive impairment affects mental functions such as memory or attention but has not addressed how limited brain-power affects physical activity like balance and walking in people with COPD.
Walking is usually considered to be fairly automatic but it often requires multitasking because we might be thinking about things while we walk (e.g., talking to a friend or what to buy at the hardware store) or manoeuvring around objects, like frost heaves in the sidewalk or furniture in our home. Recently, impaired balance and greater falls have been reported in people with COPD.4-6 Much work has focused on peripheral issues such as muscle strength, physical performance tasks and cellular attributes of muscle fibres to explain their slow walking and poor balance. However, limited functional mobility may in part be attributed to impairment of brain areas that provide input to movement and balance.
What is our research question?
As a first step to explore the brain’s contribution to multi-tasking, we monitored brain activity during single tasks and combined tasks in people with COPD. We also studied comparison groups of younger adults and an older age-matched healthy cohort. The purpose of our study was to compare dual tasks’ error to single tasks’ error while measuring prefrontal cortex oxygenated haemoglobin as a marker of neural activity in these three groups of participants.
How are we studying the problem?
Brain activity of the prefrontal cortex was evaluated by measuring oxygenated hemoglobin via functional near infrared spectroscopy (fNIRS)7,8 (see picture to the right). Increased neural activity in the prefrontal cortex (front of the brain) increases the metabolic demand of the neurons, which in turn increases blood flow to the brain region and increases the amount of oxygenated haemoglobin. We evaluated neural activity of the prefrontal cortex during walking at the participant’s usual pace and when the person walked as quickly and safely as possible. We also asked the person to spell five-letter words backwards. We then asked the participant to do two things at once – to walk at their usual pace while spelling words backwards and to walk at a very quick pace while spelling words backwards. In addition to monitoring neural activity using fNIRS, we also measured the accuracy of spelling backwards and the variability in walking. We used a Zeno pressure sensitive mat (see picture below) that has ~14,000 sensors. Using the associated software, various measures of gait such as velocity, stride length and variability of these parameters were derived. My Masters student, Ahmed Hassan, has done the majority of the work on this project. He was also assisted by my postdoctoral fellow, Dr. Karina Kasawara, and two visiting scientists, Dr. Leandro Bonetti from Brazil and Dr. Masatoshi Hanada from Japan. Dr. Kara Patterson, a colleague in the Department of Physical Therapy at the University of Toronto, has also provided substantial expert consultation.
What have we discovered?
Our sample sizes are small right now and the study is ongoing so these results are preliminary. We have found that people with COPD make more errors when spelling backwards during walking compared to simply spelling backwards. The number of spelling errors made during dual tasking in COPD participants was greater than those errors made by younger and older adults. They also walk more slowly while spelling backwards compared to walking alone. Lastly, neural activity of the prefrontal cortex increased more during dual versus single tasks in the older group and tended to increase in the COPD participants.
What next? How do we help our patients?
One of the most effective ways to improve the quality of life in people with chronic obstructive lung disease is to improve their fitness. Although people with COPD have a tendency to fall more often than other older adults, the best ways to improve balance and walking ability are not known. Although not all tested in COPD patients, several interventions have the potential to improve mobility while multi-tasking in COPD patients such as virtual reality and complex obstacle training simulations. Even aerobic training can increase cognitive function in the elderly9 so this intervention alone, in our COPD clients, has the potential of improving their function in more complex situations.
We are grateful to the ORCS of The Lung Association – Ontario who provided us with funding in 2017-18 to perform this study. We also very much appreciate the contributions of the participants who devoted their time in performing this study.
Darlene Reid, a member of ORCS, is a physiotherapist and professor in the Department of Physical Therapy at the University of Toronto.