For Geriatric Falls, 'Brain Speed' May Matter More than Lower Limb Strength

When assessing an older person’s fall risk, brain processing speed matters, U-M researchers found. Which is why they invented a device for bedside use to measure that speed. 

“Why does a 30-year-old hit their foot against the curb in the parking lot and take a half step and recover, whereas a 71-year-old falls and an 82-year-old falls awkwardly and fractures their hip?” asks James Richardson, M.D., professor of physical medicine and rehabilitation at the University of Michigan Comprehensive Musculoskeletal Center.

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For the last several years, Richardson and his team set out to answer these questions, attempting to find which specific factors determine whether, and why, an older person successfully recovers from a trip or stumble. All this in an effort to help prevent the serious injuries, disability, and even death, that too often follow accidental falls.

“Falls research has been sort of stuck, with investigators re-massaging over 100 identified fall ‘risk factors,’ many of which are repetitive and circular,” Richardson explains. “For example, a 2014 review lists the following three leading risk factors for falls: poor gait/balance, taking a large number of prescription medications and having a history of a fall in the prior year.”

Richardson continues, “If engineers were asked why a specific class of boat sank frequently and the answer came back: poor flotation and navigational ability, history of sinking in the prior year and the captain took drugs, we would fire the engineers! Our goal has been to develop an understanding of the specific, discrete characteristics that are responsible for success after a trip or stumble while walking, and to make those characteristics measurable in the clinic.”

Richardson’s latest research finds that it’s not only risk factors like lower limb strength and precise perception of the limb’s position that determine if a geriatric patient will recover from a perturbation, but also complex and simple reaction times, or as he prefers to refer to it, a person’s “brain speed.” The work is published in the January 2017 edition of the American Journal of Physical Medicine & Rehabilitation.

“Our study wanted to identify relationships between complex and simple clinical measures of reaction time and indicators of balance in elderly subjects with diabetic peripheral neuropathy, nerve damage that can occur in those with diabetes,” Richardson says.

“These patients fall twice as often as people their age typically do, so we wanted to examine each person’s ability to make a decision in less than half a second, or around 400 milliseconds. Importantly, this is also about the length of time the foot is in the air before landing while walking, and about the time available to recover from a stumble or trip.”

He realized they needed a new, easy way to measure that rapid decision-making ability. 

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