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The Mini-Balance Evaluation System Test Can Predict Falls in Clinically Stable Outpatients With COPD

A 12-MO PROSPECTIVE COHORT STUDY

Pereira, Ana Carolina A. C. MSc, PT; Xavier, Rafaella F. PhD, PT; Lopes, Aline C. MSc, PT; da Silva, Cibele C. B. M. MSc, PT; Oliveira, Cristino C. PhD, PT; Fernandes, Frederico L. A. MD, PhD; Stelmach, Rafael MD, PhD; Carvalho, Celso R. F. PhD, PT

Journal of Cardiopulmonary Rehabilitation and Prevention: November 2019 - Volume 39 - Issue 6 - p 391–396
doi: 10.1097/HCR.0000000000000427
Pulmonary Rehabilitation
Free

Purpose: This study evaluated the accuracy of the Mini-Balance Evaluation System Test (Mini-BESTest) for predicting falls in patients with chronic obstructive pulmonary disease (COPD) and investigated whether postural balance is a risk factor for falls.

Methods: Postural balance was evaluated by the Mini-BESTest at baseline, and the incidence of falls over a 12-mo period was prospectively measured by a self-reported falls diary and confirmed by telephone calls. A discriminative power analysis was performed using receiver operating characteristic (ROC) curve and logistic regression analysis.

Results: Sixty-seven outpatients with COPD (mean age ± SD = 67 ± 9.3 yr) were included. Twenty-five patients (37.3%) experienced ≥1 fall, and 28.2% of the falls resulted in injuries. The Mini-BESTest predicted falls in patients with COPD at the 6- and 12-mo follow-ups with a cut-off score of 22.5 (area under the curve = 0.85 and 0.87) with good sensitivity and specificity (85.7% and 66.7%; 84% and 73.8%, respectively). Higher scores on the Mini-BESTest were associated with a lower risk of falls at 12 mo (OR = 0.50; 95% CI, 0.36–0.70; P < .001).

Conclusions: Postural balance assessed by the Mini-BESTest is a good predictor of falls in patients with COPD. Our results imply that impaired balance contributes to the risk of falling and that balance training and fall prevention programs may be required for this population.

This study demonstrated that the Mini-BESTest can be used to predict prospectively falls in COPD patients. In addition, the study describes which component of the Mini-BESTest can predict impairments in these patients. Therefore, the subcomponents of the Mini-BESTest could be used to target specific balance training for COPD patients.

Department of Physical Therapy, School of Medicine, University of São Paulo, São Paulo, Brazil (Mss Pereira, Xavier, Lopes, da Silva, and Carvalho); Department of Physical Therapy, Life Sciences Institute, Federal University of Juiz de Fora-GV Campus, Minas Gerais, Brazil (Dr Oliveira); and Pulmonary Division, Heart Institute (InCor), Hospital das Clínicas da Faculdade de Medicina da USP, São Paulo, Brazil (Drs Fernandes and Stelmach).

Correspondence: Celso R.F. Carvalho, PhD, PT, Department of Medicine, School of Medicine, University of São Paulo, Av. Dr. Arnaldo 455, Rm 1210, 01246-903, São Paulo, SP, Brazil (cscarval@usp.br)

The authors declare no conflicts of interest.

Chronic obstructive pulmonary disease (COPD) is a common, preventable disease characterized by persistent respiratory symptoms and airflow limitation.1 Impaired lung function is the main marker of severity in COPD; however, several systemic manifestations also occur, with detrimental effects on patient quality of life and prognosis.2 These systematic manifestations include peripheral muscle weakness as well as reduced functional mobility and exercise capacity.3,4 Recent studies demonstrate that patients with COPD present with postural balance impairment and high risk of falls.5–7

Older adults have a high risk of death or serious injury arising from accidental falls, which impose considerable costs on health care systems worldwide.8 Some factors, including medication use, muscle weakness, and reduced mobility, may contribute to postural balance impairment and consequently to this increased risk of falls.9 Patients with COPD also present with these risk factors, which may explain the increased risk of falls in this population.10 It is estimated that 40% of patients with COPD fall at least once in a given year while this prevalence is approximately 33% in community-dwelling older adults without lung disease.11,12 Falls may also contribute to the occurrence of vertebra and femur fractures in patients with COPD,13 who may have 60% to 70% higher risk of death following hip fracture compared with those without the disease.14

Therefore, it is important to identify patients with impaired balance who may be at an increased risk of falls. A few tests for assessing postural balance have demonstrated adequate predictive validity to identify those with an increased fall risk.15 The Mini-Balance Evaluation System Test (Mini-BESTest)16 assesses important aspects of dynamic balance control, including the capability to react to postural perturbations, to stand on an unstable surface, and to walk while performing a cognitive task. Assessments of these balance components may influence the performance during activities of daily living.17,18 The Mini-BESTest is an easily performed instrument applicable to clinical practice and has predictive validity for falls in patients with neurological disorders.19–21 In patients with COPD, the Mini-BESTest has excellent interrater (intraclass correlation coefficient [ICC] = 0.85) and intrarater reliability (ICC = 0.88) and is able to discriminate between cross-section fallers and nonfallers.22 However, to the best of our knowledge, no study has investigated the Mini-BESTest's validity in predicting falls in patients with COPD, which could yield more precise estimates of fall risk in this population.

The present study aimed to assess the accuracy of the Mini-BESTest to prospectively predict falls in clinically stable COPD outpatients over a 12-mo period. The accuracy of the Mini-BESTest for predicting falls over a 6-mo period and the test subcomponents associated with a lower risk of falls in this population were also investigated.

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METHODS

STUDY DESIGN

This is a prospective cohort study with a 12-mo follow-up. All patients performed the initial assessments at 2 visits within a 2-wk period. Demographic, anthropometric, clinical data, pulmonary function, and postural balance were assessed. After the initial assessments, patients were instructed to complete a monthly falls diary to report the number of falls over a 12-mo period. The initial evaluation was performed by experienced physiotherapists trained to use the Mini-BESTest. An experienced researcher was trained for falls data recording and had no prior knowledge of the study data analysis.

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PARTICIPANTS AND SETTING

Seventy consecutive patients with COPD were recruited from a tertiary university hospital between March and December 2015. Inclusion criteria were (1) COPD diagnosis1; (2) clinical stability for, ≥1 mo prior to the study1; and (3) smoking history >10 pack/yr. Exclusion criteria were (1) the use of continuous oxygen therapy; (2) symptomatic cardiovascular disease; (3) severe neurological or musculoskeletal conditions known to interfere with postural balance; (4) inability to understand the study procedures; (5) participation in an exercise program 6 mo prior to participation in the study; or (6) untreated visual abnormality. The study was approved by the Research Ethics Committee of the institution (protocol #940.589).

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DATA COLLECTION PROCEDURES

Demographic, Anthropometric, and Clinical Data

Patient characteristics, smoking history, the number of comorbidities, and history of falls over the past 12 mo were obtained from an initial interview and the patient medical records. Dyspnea was assessed by the modified Medical Research Council dyspnea scale (mMRC).23,24 Spirometry was performed according to the American Thoracic Society/European Respiratory Society guidelines,25 and Brazilian population normative values were used.26

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Postural Balance

The Mini-BESTest was used as clinical balance assessment. The test consists of 14 items grouped into 4 domains: anticipatory postural adjustments (sit-to-stand, rise to toes, and standing on 1 leg); postural responses (compensatory stepping reactions in forward, backward, and lateral directions); sensory orientation (stance on a firm surface with eyes open, on a foam surface with eyes closed, and on an inclined surface with eyes closed); and gait (change in gait speed, walking with head turns, walking with pivot turns, stepping over obstacles, and the time to “get up and go” with dual tasks). Each item is scored from 0 (unable or requiring help) to 2 (normal), with a total score of 28 points and higher scores indicate better balance performance.16,27 The Mini-BESTest has been adapted and translated into Brazilian Portuguese and has shown adequate reliability (ICC = 0.99 and 0.95), construct, and discriminant validity.28

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Falls

Falls were evaluated monthly using a 12-mo self-reported falls diary during the follow-up period. The calendars were returned during the outpatient medical visits. The following definition of a fall was used: “an unexpected event in which the participants come to rest on the ground, floor, or lower level.”29 In addition, every fall recorded was followed by a telephone call performed by the same trained researcher on falls recording for consistency. This standardized interview was conducted during the telephone calls to confirm fall occurrence and to clarify about the nature of the fall, including location, cause, activities performed and symptoms at the time of the fall, need for health care assistance, and injuries. Patients who reported ≥1 fall during the follow-up period were called fallers. Patients were classified as recurrent fallers (RF) if they reported at ≥2 falls within 6 mo during the 12-mo follow-up period.

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STATISTICAL ANALYSIS

All statistical analyses were obtained using the Statistical Package for the Social Sciences (SPSS v23.0; IBM) and graphic plots were created using GraphPad Prism 5.0 (GraphPad Software). A sample size of 59 patients was required on the basis of an expected prospective prevalence of falls of 40% in patients with COPD,10 for 95% confidence and precision (d) of 0.05. The final sample of 70 participants would be required to apply the finite population correction, as n/N was >0.05, and keep the desirable level of confidence and precision.30 To assess the predictive validity of the Mini-BESTest for falls at 6 and 12 mo, the receiver operating characteristic (ROC) curve and the area under the curve (AUC) were determined.31 The AUC was interpreted as follows: AUC = 0.5 no discrimination; 0.7 ≤ AUC <0.8 acceptable; 0.8 ≤ AUC <0.9 excellent; and AUC ≥ 0.9 outstanding level of discrimination.32 The optimal cut-off score was chosen as the intersection point that maximized both the sensitivity and specificity values. Positive and negative likelihood ratios (LR+ and LR−, respectively) were also determined.33 Logistic regression analysis was used to investigate the role of the Mini-BESTest total score and its domains as risk factors for falls. A model adjusted for age and the number of comorbidities was also explored. ORs with 95% CIs were calculated for each variable. A P value < .05 was considered statistically significant.

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RESULTS

One hundred twenty-seven patients with COPD were assessed for eligibility: 70 met the inclusion criteria, and 67 (95.7%) completed the 12 mo follow-up for falls. Deaths were the cause for noncompletion. The study flow diagram is shown in Figure 1 and participant characteristics are reported in Table 1.

Figure 1

Figure 1

Table 1

Table 1

The prevalence of falls at 6- and 12-mo follow-up was 21 (31.3%) and 25 (37.3%), respectively. The number of RF was 13 (61.9%) and 16 (64%), respectively, at the same time points. Most falls occurred indoor (47.9%) while performing upper limb activities in the standing position (26.8%). Loss of balance was self-reported as the main cause in 22.5% of falls. Most of the fallers (73.2%) reported being concerned about recurrent falls. Figure 2 shows the frequency of fallers and RF during the 12-mo follow-up. The highest proportion of new fallers was observed in the first 3 mo. In contrast, the proportion of RF increased over the follow-up period, particularly from the 10th mo to 12th mo.

Figure 2

Figure 2

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FALL PREDICTION USING THE MINI-BESTest

The Mini-BESTest predictive validity analysis and the cut-off scores for falls prediction at 6- and 12-mo follow-up are presented in Table 2. The ROC curves for both time points are shown in Figure 3. The AUC indicated excellent discriminant ability (0.85 and 0.87) of the Mini-BESTest for identifying fallers at both time points. The sensitivity was 85.7% and 84%, and specificity was 66.7% and 73.8%, at the 6- and 12-mo follow-up, respectively. The cut-off score of 22.5 was identified as the optimal cut-off value for both time points to discriminate fallers from nonfallers (Table 2).

Figure 3

Figure 3

Table 2

Table 2

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RISK OF FALL USING THE MINI-BESTest TOTAL AND DOMAIN SCORES

The association between the risk of falling and postural balance based on the total and domain scores of the Mini-BESTest over the 12-mo follow-up is described in Table 3. A higher Mini-BESTest total score was significantly associated with a lower risk of falls at 12 mo (OR = 0.50; P < .001). After adjustment for age (an established fall risk factor in the elderly) and the number of comorbidities, this association remained significant (OR = 0.49; P < .001). Moreover, higher scores for the Mini-BESTest domains of anticipatory postural adjustment (P < .01), postural responses (P < .001), and balance during gait (P < .001) were also independently associated with a decreased risk of falls in patients with COPD.

Table 3

Table 3

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DISCUSSION

This is the first prospective study to demonstrate the validity of the Mini-BESTest in predicting falls in patients with stable COPD. Our findings showed that the Mini-BESTest is an accurate instrument and a good predictor of falls in patients with COPD at 6 and 12 mo. In addition, a higher total score and higher scores on the anticipatory postural adjustment, postural responses, and balance during gait domains of the Mini-BESTest were associated with a lower risk of falling in this patient population.

The Mini-BESTest was used in this study because it evaluates both dynamic balance control and stability during complex gait activities. People with COPD may have a greater risk of falling during dynamic tasks such as walking, those requiring anticipatory postural adjustments or reliance on the musculoskeletal system.7 The Mini-BESTest evaluates anticipatory postural adjustments, reactive postural control, and balance during the gait; therefore, it encompasses the balance components more affected in COPD. In addition, the Mini-BESTest is applicable to clinical practice compared with laboratory-based balance assessment tools. The Mini-BESTest is acceptable for use with older people34 and is able to predict falls in patients with Parkinson's disease.19,20 A recent study showed that several balance tests, such as the BESTest, the Mini-BESTest, the Brief-BESTest, and the Berg Balance Scale (BBS), had acceptable abilities to differentiate patients with and without a history of falls.22 Specifically, the Mini-BESTest was able to identify the retrospective fall status in patients with COPD using a cut-off point of 21.5 (sensitivity of 68% and specificity of 65%).22 Our study showed a Mini-BESTest cut-off point of 22.5, with higher values of sensitivity and specificity (84% and 73.8%, respectively) using a prospective design. In addition, our study evaluated a larger sample (67 vs 46 patients with COPD). Establishing a cut-off for falls prediction is important to identify patients who may require greater attention and specific treatment for postural control impairment.

In this study, a fall prevalence of 37.3% over 12 mo was observed. These findings support previous retrospective35–37 (from 27.8% to 46%) and prospective10,38 (from 31.7% to 40%) investigations in people with COPD. Our study also showed that most patients fell in the first 3 mo after initial balance evaluation and the prevalence of RF increased in the following months. We observed a prevalence of 64% of RF at the 12 mo follow-up, which is in agreement with previous studies (41% and 75%).10,38 Interestingly, the incidence of RF in patients with COPD is comparable to those observed in patients with Parkinson's disease (58.5%).20 Repeated falls may lead to a substantial economic burden on the health system because of multiple visits at the emergency department and hospital admissions39; thus, an earlier identification of the RF in the COPD population is very important.

Furthermore, a better postural balance performance was associated with a decreased fall risk in patients with COPD. A previous study showed a correlation between worse postural control and frequency of falls in patients with COPD.36 In addition, those who fall had poorer functional mobility than the nonfalling patients.35,37 However, in most studies, falls were collected retrospectively. International guidelines for preventing and reducing falls in older adults emphasize the importance of a reliable prospective falls analysis.29 Thus, our prospective study likely provides more consistent data on the falls risk factors and prevention in people with COPD.

Oliveira et al10 showed that postural balance was independently associated with an increased incidence of falls; this did not remain after the inclusion of other predictors in a multivariate analysis. In our study, postural balance remained a significant risk factor for falls after controlling for age and the number of comorbidities. In both studies, falls were evaluated prospectively; however, Oliveira and colleagues included a smaller number of participants and used a different postural balance assessment tool, the BBS. Unlike the Mini-BESTest, the BBS does not include important aspects of dynamic balance control. This finding corroborates previous suggestions on the BBS ceiling effect in the COPD population and may have constrained the ability to identify those with higher balance function in previous investigations.10,40

Better performance on the anticipatory postural adjustment, postural responses, and balance during gait domains of the Mini-BESTest was associated with reduced fall risk. The ability to maintain balance in daily life requires a combination of anticipatory and compensatory postural strategies.41 The anticipatory control reduces the effect of a predictable disturbance, while compensatory control is the only resource of stability for unexpected perturbations.42 A previous study showed that patients with COPD are unable to react quickly in circumstances of postural instability.7 These patients also demonstrated more pronounced deficits in the biomechanics, the anticipatory postural adjustment, and the gait domains of the BESTest compared to age-matched control subjects.7 Furthermore, changes in gait components, such as reduced step length, increased time spent in double support, and worse gait rhythm, are associated with an increased fall risk in COPD.42,43 Our findings confirmed these previous investigations and determined a direct association between anticipatory postural adjustment, postural responses, and balance during gait and a reduced risk of falls. These results suggest that patients with decreased postural response on dynamic balance components can benefit from training to increase stability during postural transitions (eg, sit-to-stand, changes in the base of support) and gait training.

Therefore, the assessment of postural balance using the Mini-BESTest can be a useful tool for determining interventions targeted to specific deficits and prevent future falls in patients with COPD. Balance training, including posture, transition, and gait exercises in addition to functional muscle strengthening, has been found to be feasible and effective44 as part of pulmonary rehabilitation and have a positive effect on balance performance in COPD.44,45 Further studies are required to determine the use of the Mini-BESTest as a fall predictor in a specific group of patients who may be at an increased risk, including those on supplemental oxygen and those experiencing acute exacerbation.

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LIMITATIONS

First, we included only clinically stable outpatients; therefore, our findings cannot be generalized to patients on supplemental oxygen, hospitalized patients, or those experiencing an acute exacerbation. Second, we used a clinical instrument for balance assessment that is considered less sensitive and precise for detecting changes in postural balance than laboratory tools.15 However, the Mini-BESTest is less expensive, more accessible in clinical practice and does not require a specialized training prior to administration. Third, the Mini-BESTest evaluates only 4 out of 6 domains from the original BESTest, and other 2 aspects of balance impairment in COPD might have been investigated. However, the Mini-BESTest does not contain redundant items as its full version of the test or have a ceiling/floor effect as balance assessment tools recommended for COPD.15 Of note, the Mini-BESTest takes only 10 to 15 min to administer and has well-documented clinimetric properties in patients with COPD.16,22

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CONCLUSIONS

This is the first prospective study to demonstrate the good sensitivity and specificity of the Mini-BESTest for predicting falls in clinically stable outpatients with COPD using a cut-off score of 22.5 in the medium- and long-term. The balance impairment in people with COPD contributes to a risk of falling, specifically the impairment in anticipatory postural adjustments, postural responses, and gait.

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ACKNOWLEDGMENTS

This work was supported by the São Paulo Research Foundation (FAPESP) (grant #201605968-1 and #2013/20676-9).

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Keywords:

COPD; postural balance; rehabilitation; risk factor; ROC curve

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