Perturbation training can reduce community-dwelling older adults' annual fall risk: a randomized controlled trial

Abstract

Background: Previous studies indicated that a single session of repeated-slip exposure can reduce over 40% of laboratory-induced falls among older adults. The purpose of this study was to determine to what degree such perturbation training translated to the reduction of older adults' annual falls risk in their everyday living.

Methods: Two hundred and twelve community-dwelling older adults (≥65 years old) were randomly assigned to either the training group (N = 109), who then were exposed to 24 unannounced repeated slips, or the control group (N = 103), who merely experienced one slip during the same walking in the same protective laboratory environment. We recorded their falls in the preceding year (through self-reported history) and during the next 12 months (through falls diary and monitored with phone calls).

Results: With this single session of repeated-slip exposure, training cut older adults' annual risk of falls by 50% (from 34% to 15%, p < .05). Those who experienced merely a single slip were 2.3 times more likely to fall during the same 12-month follow-up period (p < .05) than those who experienced the 24 repeated slips. Such training effect was especially prominent among those who had history of falls.

Conclusion: A single session of repeated-slip exposure could improve community-dwelling older adults' resilience to postural disturbances and, hence, significantly reduce their annual risk of falls.

Keywords: Generalization; Inoculation.; Learning-from-falling; Postural disturbance; Retention.

Figure 1.

(a) Schematics of the experimental setup used to induce an unannounced slip in the person traversing the walkway. A slip is induced by releasing two low-friction movable platforms embedded in the middle of this 7-m walkway. Each of the two moveable platforms is mounted to the walkway base frame with four low-friction linear bearings. The base frame is bolted to two force plates (not shown) that are used to measure ground reaction force; each platform is unlocked electronically after the force plates detect the landing of the corresponding foot. All participants wore a safety harness adjusted to prevent any part of the body (other than the feet) to come in contact with the ground. (b) The protocol of the initial session for (A) the training group and (B) the control group. Participants were never told the forthcoming trial condition; rather, they were only informed that a slip “may or may not occur.” To make the timing of the novel slip trial difficult to anticipate, the first 10 trials for everyone was unperturbed (regular) trials in which the low-friction platforms were firmly locked in place. The training group then experienced a total of 24 slips delivered in a block-and-mixed fashion. Two blocks of eight slip trials are shown in gray, intervening two blocks of three nonslip (NS) trials in white, and a final block of mixed eight slip and six nonslip trials in vertical lines. The control group only experienced the novel (single) slip.

Figure 2.

Video sequences show three possible slip outcomes: (a) a participant experienced a fall, the same participant recovered successfully in the subsequent slip trials, (b) with a skate-over strategy, and (c) with a walkover strategy (25). Three frames in a1–a3, b1–b3, and c1–c3 show the instants of foot touchdown that triggered the onset of the slip, postslip liftoff, and touchdown of trailing limb. The triangle on each frame marks the location of the heel at the onset of the slip.

Figure 3.

Flowchart of the number of the participants in various phases of the study. Of 269 older adults (≥65 years) recruited from communities around the Greater Chicago Area, 51 participants did not continue due to poor bone density, five due to poor mobility, and one due to poor cognition/memory. The remaining 212 were randomly assigned to one of the two groups. The intervention in the initial session consisted of repeated exposure to a total of 24 slips for the training group, whereas the control group only experienced a single slip. In the next 12 months, 142 of them completed the falls monitoring program, and the results from 67 and 75 participants were analyzed for the training group and the control group, respectively.

Figure 4.

(a) Rate of falls (%) during the first slip for the training group (filled circles) and the control group (open squares) and during the final (24th) slip in the initial session. (b) Annual rate of self-reported falls both groups experience in everyday living prior to the initial session (history) and in 12 months following the initial session (prospective). * indicates a significance level of p < .05, **p < .01, and ***p < .001.

Figure 5.

(a) On-treatment analysis of Kaplan–Meier survival curves of falls during the 12-month fall-monitoring program. (b) Intention-to-treat analysis of Kaplan–Meier survival curves of falls during the 12-month fall-monitoring program.