Thirty-five of the 53 subjects demonstrated differences in BBS scores between the first and second trials: 29 scored lower on the BBS while wearing the shoulder immobilizer, whereas only 6 scored lower on the BBS without the immobilizer. The Wilcoxon signed-ranks test (Table 3) indicated a significant difference between paired observations (z = −4.177, P < .0001).
Eighteen of the 53 subjects (34%) exhibited no difference in scores (ie, the use of an immobilizer did not adversely affect balance), and 9 of these 18 subjects (50%) achieved the highest possible score (56) during both test conditions. Balance may have been affected in these 9 individuals, but the BBS may have failed to detect any changes because of a ceiling effect. In examining characteristics of these 9 individuals, the mean age was 70.9 (range, 66-79) years, 6 of 9 were women, and 1 of 9 had fallen within the past 6 months. In general, this group of 9 was younger than the total group (mean age = 70.9 vs 75.4), had fewer women (67% vs 74%), and had fewer falls (11% vs 26%).
When comparing participants with history of falls (n = 14) with participants with no history of falls (n = 38), the mean (SD) change scores were similar for the 2 groups: −0.93 (1.2) for the participants with history of falls and −1.05 (1.7) for the participants with no history of falls. Of the 53 subjects, 33 wore shoulder immobilizers during the first trial and 20 wore immobilizers during the second trial. Of the 20 subjects who wore the immobilizer during the second trial, scores increased for 15% (3/20), decreased for 50% (10/20), and stayed the same for 35% (7/20). Of the 33 subjects who wore the immobilizer during the first trial, scores increased for 55% (18/33), decreased for 12% (4/33), and stayed the same for 33% (11/33).
We did not conduct a reliability trial prior to the study to determine reliability of our raters; however, others have found good to excellent interrater reliability for the BBS.18,20,21,24 As in our study, Holbein-Jenny et al20 also used student physical therapists as raters in a study assessing balance in older adults and reported good interrater reliability (ICC = 0.88).
We attempted to control for order of testing through random assignment, but we did not have equivalent numbers of subjects for the 2 trials: 33 wore shoulder immobilizers during the first trial and 20 wore immobilizers during the second trial. We were concerned that there might be a learning effect and that participants would perform better on the second trial regardless of the use of shoulder immobilizers. While we recommend that future researchers attempt to control for order of testing, we believe that any learning effects between the first and second trials in our study were minimal.
We did not conduct a power analysis a priori because there is limited information on power analysis for nonparametric testing.25 In fact, Portney and Watkins26 state that power analysis with nonparametric testing is not necessary when significant differences are found and the null hypothesis is rejected.
We chose to use the BBS because it requires minimal equipment (a stopwatch, step, 2 chairs, and a ruler), can be administered in less than 20 minutes, and can be performed in a clinical or nonclinical setting. It was initially tested on an older adult population with documented balance impairments18 but has been used to assess balance in patients with stroke24 and with residents of personal care homes20 to determine if functional balance is associated with falls in older persons with history of hip fracture,27 to predict falls in older persons,21 and to screen inner-city community-dwelling older adults.28 One concern with BBS testing is rater bias. We were unable to blind raters to testing condition; therefore, rater bias may have occurred because the same tester took both measurements. Raters may have been influenced to score subjects lower on the BBS when wearing the immobilizer because of a preconception that balance might be worse under this condition.
Although we did not restrict participation in our study on the basis of race and gender, our sample was limited to non-Hispanic white, predominantly female, and older adults. This group of individuals may not reflect the general characteristics of all community-dwelling, older adults. Therefore, we cannot generalize the results of our study.
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