Sometimes the clue to an older adult’s health is not hidden in a complex blood test, an expensive scan or a long list of medical diagnoses. It may appear in a basic daily function many people take for granted: how quickly an older person can take a single step.
A study conducted at Ben-Gurion University of the Negev suggests that the speed of a voluntary step, especially when performed under distraction, may serve as an important clinical marker of functional health, independence and even long-term survival in older adults. The findings were published in the journal Gerontology.
“For the past 25 years, my research has focused on balance and gait control, with an emphasis on older adults, and even more specifically on falls among older adults,” said Prof. Yitzhak Melzer of Ben-Gurion University’s Department of Physical Therapy, who led the study. “This is a very serious global problem. About 30% of adults over 65 fall at least once a year, and about 50% of those aged 80 and older. In Israel, around 1,000 older adults arrive in emergency rooms every day because of a fall. Some suffer a hip fracture. The costs to the health system are enormous. In the United States alone, it amounts to about $50 billion a year.”
According to Melzer, the major challenge is not only treating people after a fall, but identifying in advance who is at high risk.
“Falls cannot be prevented 100%, but we can identify those who need help and treat them in a personally tailored way,” he said. “If, out of the entire older population, we can identify the 30% who are at high risk of falling, we can intervene in time and prevent many cases. They can be trained and their balance can be improved, medical treatment can be adjusted, medications can be added or reduced and the home environment can be adapted. Some people fall in the shower, while others trip over a rug.”
The current study was based on data collected between 2005 and 2011 in Melzer’s laboratory. During those years, participants underwent a series of balance, posture and gait tests. Among other things, researchers measured body sway while standing, meaning how well a person maintains stability while standing still, as well as a voluntary step test, in which a person stands, receives an external signal and is asked to take one step forward as quickly as possible.
“We measured something called postural sway,” Melzer explained. “When you stand with your feet together and try not to sway, you are still swaying all the time. That is normal, because our physiological system is working and monitoring balance according to the position of the feet on the ground. We are not wooden logs.
“We also tested another measure: the speed of the voluntary step. The person stands, receives a clear signal and is instructed: when you feel the stimulus, take one step as fast as you can. It is like the Olympics, when runners hear the starting shot and begin to run.”
The researchers then wanted to see what happens when that seemingly simple action is performed under cognitive load. Participants therefore performed the step test in two conditions: once without distraction, and once while completing a Stroop test.
In that task, words naming colors are shown in ink that does not match the word. For example, the word “green” may appear in yellow ink, and the participant must say the color of the ink rather than read the written word.
“The goal was to distract attention from the motor performance, in other words, to keep the brain busy, while also asking them to perform a motor action,” Melzer said.
The twist came 15 years later
Fifteen years later, the researchers returned to the same data and examined participants’ long-term survival: who was still alive and who had died. The goal was to determine whether measures that had been collected in real time, using relatively simple balance and functional tests, could also predict mortality risk years later.
“We had a twist in the plot here,” Melzer said. “We took all the data of the older adults who participated in studies in the lab between 2005 and 2011, and asked what happened to them 10, 15 and even 17 years after the initial test. The Helsinki Committee approved our review of the existing data regarding survival and mortality, and in Israel these data are very orderly. We found that about half of the people we tested died during the follow-up period.”
From there, the researchers turned to the central question: Did older adults who responded more slowly in the step test, or showed poorer stability while standing, also tend to survive for a shorter time than peers who performed better on the same tests?
The findings showed that reaction time in the step test under dual-task conditions was a significant predictor of mortality. Each 0.1-second slowdown in reaction time was associated with an approximately 28% increase in mortality risk during the follow-up period.
“To illustrate what this means in simple terms, imagine two people of the same age tested on the same day,” Melzer said. “If one of them was 0.1 seconds faster in performing the voluntary step under dual-task conditions, then according to the study model, that person’s survival expectancy was longer by about 2.9 months on average compared with the slower participant, assuming a 10-year follow-up period after the test.”
The findings underscore that it is not only the speed of the voluntary step that matters, but also the ability of the brain and body to respond quickly when required to handle two tasks at once.
“This ability reflects the integration between cognitive and motor functions, which may serve as a sensitive marker of general health and successful aging,” Melzer said. “Beyond that, in real life, during the day-to-day routine, we are constantly required to perform dual tasks: walking and talking at the same time, crossing the road while watching the traffic light so it does not change too soon, and more.”
Walking speed is already known in medical literature as an important marker of health in older age. One prominent study in the field, published in JAMA in 2011 and led by researcher Stephanie Studenski, analyzed data from more than 32,000 adults aged 65 and older. The researchers found that faster walking speed was associated with better survival. Each increase of 0.1 meters per second in walking speed was linked to an approximately 12% decrease in mortality risk during the follow-up period.
Melzer cites that study as an important starting point for understanding the current findings.
“Studenski examined walking speed among tens of thousands of older adults in a huge study,” he said. “They measured walking speed with a simple stopwatch and found that older adults who walked faster died later. Again, it sounds like common sense, but it was a very significant finding.”
Identifying functional decline before the fall
The clinical implications of the findings may be broad. Today, physicians and health systems tend to assess risk based on age, underlying diseases, medications and laboratory tests. The study suggests that simple functional measures can add an important layer of information, showing how a person’s body and brain function in real time.
“The voluntary step test is very simple to perform, and it has the ability to serve as an accessible indicator of functional vitality and increased fall risk,” Melzer said. “It combines the capacity of the neuromuscular system with cognitive processing ability, and therefore it can be an important part of a clinical assessment.”
According to Melzer, the fact that the most significant difference appeared specifically under distraction is not coincidental.
“Because basic nerve conduction and sensory detection speeds remain similar between a simple step and a step performed under distraction, any delay in initiating the step during a mental or cognitive challenge largely stems from limitations in central neural processing, meaning slower processing speed,” he said. “The integration of motor and cognitive tasks in standard clinical assessments can improve the ability to predict independence and life expectancy, and help guide early interventions focused on cognitive-motor health.”
Still, the researchers caution against drawing overly far-reaching conclusions. The study found an association between step performance and survival, but it does not prove that improving step speed in itself will extend life. In other words, it cannot be said that a specific training program will add years to a person’s life.
What can be said cautiously is that the measure may help identify functional decline earlier, and that such indicators may help doctors, physical therapists and health systems intervene clinically in time.
Melzer is already thinking about the next stage. In an earlier study conducted in his lab, researchers succeeded in improving balance and voluntary step speed in older adults through training.
“In 2015, we conducted another study in which we trained older adults in balance and walking exercises,” he said. “At the time, we looked at the improvement and said it was nice, but we did not see it as something dramatic. Today, when I look at those data, I ask myself: If I improved this measure for them, did I perhaps also cause them to live longer? That is an answer I still cannot give scientifically, but it is definitely an important question. The open question is whether such improvement also translates into improved survival. Did the lifespan of those who improved increase as a result?”
He compared the question to familiar medical markers.
“If you test blood pressure or diabetes and do not treat them, it is clear that mortality risk rises. And if you treat them, lose weight, change your lifestyle and balance the measures, you can influence a person’s future health and probably also their lifespan,” he said. “Could physiological and functional training programs do something similar? My assumption is yes, but it needs to be proven scientifically.”
Melzer now plans to expand the research to larger populations in Israel and abroad.
“At the moment, we have results from only 120 older adults,” he said. “In the future, we would like to examine larger samples through collaborations with European and American researchers, and propose this as a broader project. This test is relatively simple to perform in the lab, and if it can predict lifespan and future function, it has very great importance.”
The research group also included Ofri Ganz-Or, a student in Ben-Gurion University’s Department of Physical Therapy; Dr. Anat Reiner-Benaim of Ben-Gurion University’s School of Public Health; Yuly Treger of the Department of Rehabilitation at Soroka University Medical Center; and Lars Oddsson of the University of Minnesota.