In our daily lives, we often require the brain to work on two independent and unrelated tasks. This combined activation of the brain for two activities, such as walking and mental counting, is known as "dual tasking" as opposed to "single tasking", which involves performing only one activity. A study published in the journal The Lancet Healthy Longevity, carried out as part of a collaboration between the Institut Guttmann and researchers at Harvard Medical School (Boston, USA), indicates that the ability to switch from performing a single task to performing two tasks simultaneously decreases after the age of 54, and that this ability is conditioned by the cognitive function of each person.

Dual task performance depends to a large extent on cognitive abilities, especially the brain's ability to work through information without losing track of what we are doing and the speed at which it can process this information. For this study, the researchers analysed the dual task cost, i.e. the difference in performance when we switch from performing one task to two. "Factors such as walking speed or the variation between steps are measured, because while you are doing a task you are subtracting more resources to calculate and this leads to a more inconsistent pace of walking," explains Gabriele Cattaneo, a researcher at the Institut Guttmann and first author of the study.

Possible marker of cognitive changes

The study was conducted with 640 adults aged 42 to 64 years belonging to the Barcelona Brain Health Initiative (BBHI) cohort, a project of the Institut Guttmann aimed at learning and understanding how we can maintain brain health over time. Each participant performed 45 seconds of leisurely walking and 45 seconds of walking while subtracting in threes. Based on the results, the increase in dual task cost occurs from the age of 54, a decade before what is considered the "onset of old age" at 65. According to Cattaneo, "this is relevant because the age of 50 is the age group in which most neurodegenerative diseases often begin, although without manifesting symptoms. This study shows that the dual task is not only a measure of gait, but also of age-related cognitive aspects, and could become a marker of cognitive changes in preclinical stages of pathologies that is very easy to perform, requiring only an electronic device and 5 minutes".

The researchers also found that, after the age of 54, the increase in dual task cost due to age is also 43% dependent on the cognitive function of each person, which is the set of mental processes that enable information to be received, processed and elaborated. "We have shown that cognitive function acts as a mediator. Age and dual task cost are not related independently of cognition, but the effect of age on dual task will be 43% conditioned by cognition," concludes Cattaneo.