Dementia is the main cause of disability in older people all over the world. About 47 million people are affected, with estimates this will reach 140 million by 2050. In Australia, dementia is the leading cause of death for women and the second-leading cause of death for men. Approximately 415,000 people currently live with dementia in Australia; this is expected to rise to an estimated 1.2 million by 2056.
Finding treatments is extremely important, but one of the problems in finding treatments for dementia is that by the time it's diagnosed there's already significant pathology that has built up in the brain. That's why there's so much interest among clinicians and scientists in finding early indicators for dementia.
Now, a new study by Monash researchers has looked at the way we walk as one of these indicators. Associate Professor Michele Callisaya and Professor Velandai Srikanth, supervising first author PhD student Oshadi Jayakody from the University of Tasmania, investigated whether variability from one step to the next during walking, and slow gait speed, were related to cognitive decline over time.
The study found that higher step-to-step variability was associated with greater decline in memory, and that slow gait speed predicted decline in processing speed and visual and spatial awareness. Interestingly, in people carrying the ApoE4 gene (which is associated with Alzheimer’s disease), gait speed also predicted decline in memory.
The disease affects not only memory, but a wide range of behavioural, psychological and motor skills, resulting in a loss of ability to perform activities of daily living and to maintain relationships with loved ones.
"Walking is usually taken for granted as a simple daily function – whereas we have demonstrated in our studies that it is dependent on several brain networks functioning effectively together."
Most tests now focus on cognitive testing, different types of brain scans, as well as blood biomarkers.
Senior author Associate Professor Michele Callisaya said researchers already knew that changes in walking happened with moderate to severe dementia, but it could now be considered a potential early indicator.
Much of the authors' prior work has also looked at how brain dysfunction is related to walking dysfunction.
It found that loss of brain tissue in critical areas for thinking, including the hippocampus subcortical and prefrontal region, was associated with slow gait speed.
Other research has found greater burden of beta-amyloid (thought to be involved in Alzheimer's-type dementia) is also associated with slower gait. These results suggest cognition and mobility share common brain networks, supporting the potential use of walking ability as a simple marker of poor brain health and future risk of dementia.
“Gait might be a good overall marker of ageing, pathology and the individual’s ability to cope with pathology,” Associate Professor Callisaya said.
Gait measures, combined with the usual risk assessments, could be used to help better predict risk of future cognitive decline, potentially helping in planning future care, and gait could be objectively measured as a proxy to study the effectiveness of interventions to slow the progression of dementia, she said.
Professor Velandai Srikanth said the study highlighted there's far more to gait than we thought.
“Walking is usually taken for granted as a simple daily function – whereas we've demonstrated in our studies that it is dependent on several brain networks functioning effectively together,” he said.
“Hence, we and others have begun to take the view that it may actually be a ‘super cognitive function’ itself. The simplicity with which we can measure gait and balance makes them easily applicable to a wide variety of settings as a future biomarker of dementia.”
Associate Professor Callisaya, a physiotherapist, and Professor Srikanth, a geriatrician in the Department of Medicine at Peninsula Health, will now see if they can translate the work for use in cognitive disorder and memory clinics.
“We think gait is a really good marker of somebody’s overall health status,” Associate Professor Callisaya said. “It's been shown to not only predict falls, but also hospitalisation, mortality, and now cognitive decline in specific domains.”