Being a slow walker doesn't just signify you enjoy a leisurely stroll. According to new research, walking with a slow gait could be a symptom of significant deficits in physical and cognitive health.

New findings from a longitudinal study of just over 900 New Zealanders that began back in the 1970s has found that people in their 40s who walk with a slow gait are more likely to show signs of accelerated biological ageing and compromised brain integrity.

"The thing that's really striking is that this is in 45-year-old people, not the geriatric patients who are usually assessed with such measures," says biomedical researcher Line J.H. Rasmussen from Duke University.

Rasmussen and fellow researchers examined participants from the Dunedin Study, an exceptionally long longitudinal health study that began almost five decades ago with a cohort of over 1,000 three-year-olds.

In new research assessing the health of 904 of the remaining participants at the age of 45, the team found walking speed at mid-life seems to offer a unique window into life-long ageing processes that go back all the way to childhood.

"This study covered the period from the preschool years to midlife, and found that a slow walk is a problem sign decades before old age," says Duke psychologist and neuroscientist Terrie E. Moffitt.

In the study, the 45-year-old participants that had their walking speed measured were assessed on a number of measures of everyday physical function. They were also assessed for signs of accelerated ageing – encompassing 19 different biomarkers ranging from blood pressure to dental health – and had their brains scanned via MRI.

Historical data from the longitudinal study were also considered, such as measures of neurocognitive ability based on tests conducted since the participants were children.

The results are an eye-opener, revealing that a slower walking speed in your mid–40s is associated with poor physical function and accelerated ageing – indicated by "more rapid deterioration of multiple organ systems" (based on the biomarker readings) and aligning with a separate visual analysis of participants' facial ages conducted by a panel.

Additionally, slow gait at mid-life was associated with poorer neurocognitive functioning – and not just at the time of testing.

"Remarkably, in our study, gait speed was associated not only with concurrent neurocognitive functioning in adulthood but also with neurocognitive functioning in early childhood," the authors explain in their paper.

While the Dunedin cohort did not undergo brain scans when the study began, based on today's tests, slow walkers showed on average reduced brain volume and reduced cortical thickness.

Despite limitations that the researchers acknowledge (including a lack of gait speed measurements in previous tests with the cohort, along with a lack of historical brain imaging data from the participants), the researchers say there's a lot to "unpack" in examining the link between childhood neurocognitive functioning and gait speed at midlife in future research.

"We should not assume that poor results of cognitive testing in three-year-old children in any way doom them to lifelong problems," explains geriatric medicine researcher Stephanie Studenski from the University of Pittsburgh, who wasn't involved in the study but is the author of a commentary on the research.

"But rather, look broadly at what might be contributing to poorer performance and explore strategies to ameliorate these contributors."

If we can learn to understand the nature of the links that this almost five-decades-old study seems to show, we might stand to potentially positively influence social factors that could boost biological longevity and neurocognitive function, and potentially help arrest cognitive decline.

These are, of course, very big problems to solve – but assessing gait speed even in middle-aged people could turn out to be an overlooked and important part of the solution, Studenski says.

"The human brain is dynamic; it is constantly reorganising itself according to exposures and experience," Studenski writes.

"Perhaps in this sense, brain health, reflected in brain structure, cognition, and gait speed, is not necessarily a first cause, but rather may be a consequence or mediator of lifelong opportunities and insults."

The findings are reported in JAMA Network Open.