The speed at which older adults can initiate a voluntary step, particularly when distracted, may serve as an indicator of their overall lifespan and risk of death, according to a study published in the journal Gerontology. Researchers found that for every additional 100 milliseconds it took participants to begin a step, their risk of death increased by nearly 30 percent over the follow-up period.
Researchers in Israel recruited 120 adults over the age of 65, with an average age of 78, and monitored them for 10 to 17 years. Participants were required to stand unassisted for at least 90 seconds and walk at least 10 meters to be included in the study. The study examined how balance, posture, and muscle movement were associated with survival rates.
Participants were asked to step forward, backward, and sideways as quickly as possible. They also performed a dual-task assessment, walking while simultaneously engaging in a modified Stroop task, which involves naming the ink color of words printed in mismatched colors. This assessed their ability to perform a motor task while their attention was divided.
The study found that individuals who did not survive the follow-up period took an average of 423 milliseconds to initiate a step, compared to 313 milliseconds for those who survived. Similarly, each step took non-survivors an average of 1.3 seconds, versus 1.1 seconds for survivors. Weaker balance, particularly when standing with eyes closed, was also associated with a higher likelihood of death during the study period.
Scientists believe that slower step initiation could be a marker of diminished neurological and physiological resilience in aging. This resilience reflects the brain and body's ability to adapt to stress. Poor balance, for instance, can increase the risk of falls, which in older adults can lead to serious injuries such as broken bones, muscle wasting, and traumatic brain injuries. Slower step initiation may also contribute to a cascade of mortality factors, including reduced physical activity.
Walking speed naturally declines with age due to factors such as muscle weakness, decreased joint flexibility, poorer balance, and slower brain processing. Calf muscles degrade over time, leading to shorter steps, while nerve signal delays between the brain and muscles can cause miscommunication. Age-related conditions like osteoarthritis can also cause pain, prompting individuals to slow down or increase the time between steps.
The study authors suggested that incorporating dual-task assessments into routine clinical evaluations could enhance the prediction of survival and guide early interventions focused on cognitive-motor health. However, the researchers noted limitations, including the study's small sample size and the fact that it can only demonstrate associations rather than direct causal relationships.