Walking is a complex task most commonly done while performing other tasks, like talking, reading signs, or making decisions. After the age of 65, however, such “dual-tasking” worsens walking performance for many people and may even cause unsteadiness.

A new study from Harvard Medical School and Hebrew SeniorLife published in Lancet Healthy Longevity aimed to clarify the relationships between age, dual-task gait, and cognitive function in middle age, defined as 40 to 64 years of age.

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The study found that the ability to dual-task when walking starts to decline by the age of 55, up to a decade before old age, as traditionally defined by the threshold of 65 years.

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This decline in the ability to walk and talk at the same time was found to be caused by changes in cognition and underlying brain function, not by changes in physical function.

“Our results suggest that in middle age, poor dual-task walking performance might be an indicator of accelerated brain aging or an otherwise presymptomatic neurodegenerative condition,” said first author Junhong Zhou, HMS instructor in medicine at Hebrew SeniorLife.

The paper stemmed from a collaboration between researchers at the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife and the Institut Guttmann in Barcelona, where the population-based Barcelona Brain Health Initiative (BBHI) is based. The principal investigators of the BBHI are David Batrés-Faz of the University of Barcelona and Alvaro Pascual-Leone, HMS professor of neurology at Hebrew SeniorLife.

For this research, 996 community-dwelling adults aged 40 to 64 participating in the BBHI study were recruited between May 5, 2018, and July 7, 2020.

Of these, 640 (342 men and 298 women) completed gait and cognitive assessments during the study period (an average of 24 days between the first and second visit) and were included in the analysis.

“We assessed a large number of individuals between the ages of 40 and 64 years, and observed that the ability to walk under normal, quiet conditions remained relatively stable across this age range. However, even in this relatively healthy cohort, when we asked participants to walk and perform a mental arithmetic task at the same time, we were able to observe subtle yet important changes in gait starting in the middle of the sixth decade of life,” said Zhou.