Does “Brain Speed” Cause Falling?

For many seniors, taking a bad fall can result in horrendous consequences – scrapes, fractures, pain, broken teeth, maybe even a trip to the emergency room.   This research study caught my attention because it is a new take on an old problem, measuring “brain speed” with respect to fall risk. Read on:

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.

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.

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 American Journal of Physical Medicine and Rehabilitation.

Measuring simple and complex reaction time

Using a device developed with U-M co-inventors James T. Eckner, Hogene Kim and James A. Ashton-Miller, simple reaction time is measured much like a drop-ruler test used in many school science classes, but is a bit more standardized.

The clinical reaction time assessment device consists of a long, lightweight stick attached to a rectangular box at one end. The box serves as a finger spacer to standardize initial hand position and finger closure distance, as well as housing for the electronic components of the device.

To measure simple reaction time, the patient or subject sits with the forearm resting on a desk with the hand off the edge of the surface. The examiner stands and suspends the device with the box hanging between the subject's thumb and other fingers and lets the device drop at varying intervals. The subject catches it as quickly as possible and the device provides a display of the elapsed time between drop and catch, which serves as a measurement of simple reaction time.

Although measuring simple reaction time is useful, the complex reaction time accuracy is more revealing. The initial set up of the device and subject is the same. However, in this instance, the subject's task is to catch the falling device only during the random 50 percent of trials where lights attached to the box illuminate at the moment the device is dropped, and to resist catching it when the lights do not illuminate.