PHYS THER 2011 Hergenroeder 1223 34

8/12/2019 PHYS THER 2011 Hergenroeder 1223 34

1/14

doi: 10.2522/ptj.20100214

Originally published online June 16, 20112011; 91:1223-1234.PHYS THER.

Hile, Stephanie A. Studenski and Jennifer S. BrachAndrea L. Hergenroeder, David M. Wert, Elizabeth S.Mobilityand Performance-Based Measures of Balance andAssociation of Body Mass Index With Self-Report

http://ptjournal.apta.org/content/91/8/1223found online at:The online versi on of this article, along with updated inform ation and services, can be

e-Letters

"Responses" in the online version of this article."Submit a response" in the right-hand menu under

or click onhereTo submit an e-Letter on this article, click

E-mail alerts to receive free e-mail alertshereSign up

by guest on March 8, 2014http://ptjournal.apta.org/ Downloaded from by guest on March 8, 2014http://ptjournal.apta.org/ Downloaded from
http://http//ptjournal.apta.org/content/91/8/1223http://http//ptjournal.apta.org/content/91/8/1223http://ptjournal.apta.org/letters/submit/ptjournal;91/8/1223http://ptjournal.apta.org/letters/submit/ptjournal;91/8/1223http://ptjournal.apta.org/subscriptions/etoc.xhtmlhttp://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/subscriptions/etoc.xhtmlhttp://ptjournal.apta.org/subscriptions/etoc.xhtmlhttp://ptjournal.apta.org/letters/submit/ptjournal;91/8/1223http://http//ptjournal.apta.org/content/91/8/1223


2/14

Association of Body Mass Index WithSelf-Report and Performance-BasedMeasures of Balance and Mobility Andrea L. Hergenroeder, David M. Wert, Elizabeth S. Hile, Stephanie A. Studenski,Jennifer S. Brach

Background. The incidence of obesity is increasing in older adults, with associ-ated worsening in the burden of disability. Little is known about the impact of body

mass index (BMI) on self-report and performance-based balance and mobility mea-sures in older adults.

Objective. The purposes of this study were (1) to examine the association of BMI with measures of balance and mobility and (2) to explore potential explanatory factors.

Design. This was a cross-sectional, observational study.

Methods. Older adults (mean age 77.6 years) who participated in an ongoingobservational study (N 120) were classied as normal weight (BMI 18.524.9kg/m 2 ), overweight (BMI 25.0 29.9 kg/m 2 ), moderately obese (BMI 30.034.9kg/m 2 ), or severely obese (BMI 35 kg/m 2 ). Body mass index data were missing for one individual; thus, data for 119 participants were included in the analysis. Mobility and balance were assessed using self-report and performance-based measures and were compared among weight groups using analysis of variance and chi-squareanalysis for categorical data. Multiple linear regression analysis was used to examinethe association among BMI, mobility, and balance after controlling for potentialconfounding variables.

Results. Compared with participants who were of normal weight or overweight,those with moderate or severe obesity were less likely to report their mobility as very good or excellent (52%, 55%, 39%, and 6%, respectively); however, there was nodifference in self-report of balance among weight groups. Participants with severeobesity (n 17) had the lowest levels of mobility on the performance-based measures,

followed by those who were moderately obese (n 31), overweight (n 42), and of normal weight (n 29). There were no differences on performance-based balancemeasures among weight groups. After controlling for age, sex, minority status,physical activity level, education level, and comorbid conditions, BMI still signi-cantly contributed to mobility ( .02, adjusted R2 .41).

Conclusions. Although older adults with severe obesity were most impaired,those with less severe obesity also demonstrated signicant decrements in mobility.

A.L. Hergenroeder, PT, PhD, CCS,Department of Physical Therapy,School of Health and Rehabilita-tion Sciences, University of Pitts-

burgh, 6035 Forbes Tower, Pitts-burgh, PA 15260 (USA). Addressall correspondence to Dr Hergen-roeder at: [email protected].

D.M. Wert, PT, MPT, Departmentof Physical Therapy, School of Health and Rehabilitation Sci-ences, University of Pittsburgh.

E.S. Hile, PT, PhD, NCS, Depart-ment of Physical Therapy, Schoolof Health and Rehabilitation Sci-ences, University of Pittsburgh.

S.A. Studenski, MD, MPH, Division

of Geriatric Medicine, Departmentof Medicine, University of Pitts-burgh, and VA Pittsburgh GeriatricResearch Education and ClinicalCenter.

J.S. Brach, PT, PhD, Department of Physical Therapy, School of Healthand Rehabilitation Sciences, Uni-versity of Pittsburgh.

[Hergenroeder AL, Wert DM, HileES, et al. Association of body massindex with self-report andperformance-based measures of balance and mobility. Phys Ther.2011;91:12231234.]

2011 American Physical Therapy Association

Published Ahead of Print: June 16,2011

Accepted: April 17, 2011Submitted: June 25, 2010

Research Report

Post a Rapid Response tothis article at:ptjournal.apta.org

August 2011 Volume 91 Number 8 Physical Therapy f 1223 by guest on March 8, 2014http://ptjournal.apta.org/ Downloaded from
mailto:[email protected]://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/mailto:[email protected]


3/14

Obesity is a major public health problem in the United Statesand around the world. Therehas been a substantial increase in theprevalence of obesity globally, even

in developing countries.1

In theUnited States, it is estimated thatmore than 65% of adults are overweight , dened as having a body mass index (BMI) of 25.0 kg/m 2 or higher, with more than 30% consid-ered obese (BMI 30 kg/m 2 ).Despite increased attention to thisepidemic, the prevalence of obesity continues to rise. 2,3 This increasingprevalence is of great concernbecause the health and economicburdens of obesity are vast. Numer-ous chronic diseases, includinghypertension, cardiovascular dis-ease, type 2 diabetes, osteoarthritis,and certain forms of cancer, arestrongly associated with excess body weight. 4,5 Obesity is estimated toaccount for nearly 10% of all medicalspending in the United States. 6,7 For these reasons, it is imperative thathealth care professionals be able toeffectively evaluate and treat people with conditions related to over-

weight and obesity.

The prevalence of obesity is increas-ing in older adults, with an estimated31% of those aged 60 years or older reported to be obese in 20032004. 3,8 The increased prevalence of obesity in older adults is especially concerning given the associationbetween obesity and impaired phys-ical function. 916 Physical functionrefers to a persons ability to perform

basic and instrumental activities of daily living and mobility tasks.Impairments in physical function,such as the components of mobility and balance, have been linked to thedevelopment of disability. 17,18 Analy-sis of recent trends has shown thatobesity-related disability is on therise, 19 reinforcing the need for a bet-ter understanding of the impact of obesity on mobility and balance.

The BMI is the most commonmethod to quantify weight acrossa range of body sizes in adults. 20The BMI is calculated by dividingan individuals weight (in kilograms)

by his or her height (in meterssquared). Using the BMI, individualscan be classied as underweight( 18.5 kg/m 2 ), of normal weight(18.524.9 kg/m 2 ), overweight (2529.9 kg/m 2 ), class I obese (30 34.9 kg/m 2 ), class II obese (3539.9kg/m 2 ), or class III obese ( 40kg/m 2 ). These categories of BMI were developed by the World Health Organization based on associatedhealth risks. 21 Guidelines from theNational Institutes of Health suggestthis anthropometric index should beutilized in the initial assessment of overweight and obesity. 22

The BMI is an inexpensive and easy-to-use clinical measure that can beadministered with minimal train-ing. 22 Health care professionals, such as physical therapists, may utilizethis simple measure to screenpatients and determine risks for dis-eases associated with obesity.

Although BMI is an important indica-tor of body size for use in the pri-mary care and public health domain,it is an indirect surrogate measure of adiposity and thus has several limita-tions. The BMI may overestimatebody fat in individuals with larger muscle mass, such as athletes, andmay underestimate body fat in those who have lost muscle mass (eg, older adults). 23 Furthermore, the BMIguidelines were established indepen-

dent of race, age, and sex. Studieshave shown these factors inuencethe relationship between BMI andpercentage of body fat, suggestingthe need for population-specic BMIclassications. 24,25 For these reasons,it has been suggested that the BMI beused as an initial step in the determi-nation of health risks and that thismeasure be used in conjunction with waist circumference and assessment

for the presence of concomitant risk factors. 26

The determination of an individualsBMI may assist the clinician in the

identication of risk status and con-sequently result in an intervention toreduce weight or disease risk. Inaddition to dietary restriction andbehavioral therapy, exercise is a pri-mary treatment for obesity. The pub-lic health recommendation for phys-ical activity for adults (men and women who are healthy and 18 65 years of age) and older adults (menand women 65 years of age) is aminimum of 30 minutes of moderate-intensity activity on 5 days of the week (150 min/wk). 27,28 However,there is evidence that higher levelsof exercise are needed for achieving weight loss (150 250 min/wk) andfor maintaining weight loss ( 250min/wk). 29,30 In older adults with obesity, the benets of moderate weight loss achieved through dietand exercise include improvementsin self-report and performance-basedmobility and balance measures. 31 Inaddition, studies have shown that

exercise, even in the absence of weight loss, leads to improvement inadverse health consequences associ-ated with obesity. 3234

In view of the widespread preva-lence of obesity and the critical roleof exercise and physical activity in weight loss and health risk reduc-tion, physical therapists are wellpositioned to have a substantialimpact on this signicant public

health problem. In a recent study of physical therapists knowledge of obesity, the majority believed thatidentifying obesity was within their scope of practice. 35 Furthermore,most therapists recognized that exer-cise and diet are key components of a weight loss program. Despite thesendings, the researchers concludedthat physical therapists lacked theknowledge about the use of the BMIas an indicator for identifying obesity

Association of Body Mass Index With Measures of Balance and Mobility

1224 f Physical Therapy Volume 91 Number 8 August 2011 by guest on March 8, 2014http://ptjournal.apta.org/ Downloaded from
http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/


4/14


5/14

The GaitMat II system was used tomeasure gait speed. 46 The GaitMat IIconsists of an approximately 4-m-long, pressure-sensitive walkway controlled by a computer system

that processes the data to generateboth spatial and temporal variablesof walking. On either end of the 4-m-long active walkway, nearly 2 m of inactive surface was available so thatacceleration and deceleration werenot captured in the timed walk. Gaitspeed was determined by dividingthe distance traversed by the timebetween the rst and last steps (eg,switch closure) and was recorded inmeters per second. After 2 practicepasses, each participant completed 4passes at his or her self-selected walking speed for data collection.The mean of the 4 passes was used asthe measure of gait speed.

Timed Up & Go Test. TheTimed Up & Go Test has been usedas a test of basic mobility in older adults and has been shown to havehigh intrarater and interrater reliabil-ity (ICC .90). 47,48 For this test, thetime required for each participant to

stand up from a chair, walk 3 m,turn, walk back, and sit down wasmeasured and recorded.

Six-Minute Walk Test. The 6-Minute Walk Test has been used as ameasure of mobility and aerobicendurance in older adults with and without disease and has shown to bea reliable measure (ICC .90). 49 Each participant was asked to walk as far as possible in 6 minutes, taking

standing rest periods as needed. A straight path of 15.24 m (50 ft) wasused. The total distance walked back and forth in 6 minutes was recorded.Each participants heart rate, bloodpressure, rating of perceived exer-tion, and signs and symptoms weremonitored before and after testing.

Timed chair stands. Chair standshave been utilized as a performance-based measure of lower body func-tion and have been shown to havegood reliability in older adults

(ICC .80).50

Participants wereseated in a rigid chair, asked to foldtheir arms across their chest, andstand up straight as quickly as possi-ble 5 times. The time to complete 5repeated stands from the chair wasrecorded.

Performance-Based Measures of BalanceTimed balance measures. Par-ticipants were asked to maintaintheir balance for up to 30 secondsunder each of the following condi-tions: standing with eyes closed while the feet were positioned asclose together as possible, tandemstance in which the heel of one foot was directly in front of and touchingthe toes of the other foot, and single-leg stance where the participants were asked to lift one foot off theground and maintain their balanceon the remaining leg. The rst 2 testsare a modication of standard bal-

ance tests used in the EstablishedPopulations for Epidemiologic Stud-ies of the Elderly (EPESE) project. 51In the current study, times for each trial were extended from 10 to 30seconds, and no support was provided to attain the test position.Interrater reliability (ICC .9) andtest-retest reliability (ICC .7) havebeen demonstrated for the EPESEbattery of tests. 52 In a previous study of older adults who were high func-

tioning, change of the reliability coefcient of single-leg stance wasshown to be .69. 50

Postural responses. The posturalstress test was used to test posturalresponses to a destabilizing forceapplied manually by an examiner in3 different directions (posteriorly,right, and left). Previous research hasshown that older adults classied asfallers score lower on postural

response tests compared with older nonfallers and young adults. 53 Theability of the participants to remainupright and their response whennudged at the pelvis in various direc-

tions were graded. The response was graded using the followingscale: 0 responds (single step); 1responds (multiple steps); 2responds but requires support to sta-bilize; and 3 no obvious response,individual must be supported. Theresponses to 6 perturbations, 2 ineach of the 3 directions, weretotaled, with higher scores indicat-ing greater impairment.

Narrow walk test. As previously described by Bandinelli et al, 54 par-ticipants were asked to walk a dis-tance of 4 m at their usual walkingpace within a 15-cm-wide path marked on the oor with tape. Thetime taken to complete the task wasrecorded. The number of deviationsfrom the 15-cm-wide path was alsorecorded. Individuals who could notcomplete the test independently, or who stepped outside the walkway more than 10 times, were classied

as unable. The test-retest reliability of this measure (ICC .76) has beendemonstrated in a sample of older adults. 54 Concurrent validity of thenarrow walk test has been estab-lished based on moderate to strongcorrelations with other measures of physical performance, such as gaitspeed and the 400-m corridor walk,in a sample of older adults. 55

Obstacle walk test. As previously

described by Bandinelli et al,54

par-ticipants were asked to walk a 7-mcourse at their usual walking paceand step over 2 obstacles of differentheights. One obstacle was 6 cm talland positioned 2 m from the startingline, and the other obstacle was 30cm tall and positioned 4 m from thestarting line. The time taken to com-plete this task was recorded. Theobstacle walk test has shown to be a E.Q. Inc, PO Box 16, Chalfont, PA 18914-

0016.




6/14


7/14

Physical activity habits. Duringadministration of the Survey of Activ-ities and Fear of Falling in theElderly, 57 participants were asked whether they currently walk for exercise. Because walking is themost common form of exercise for older adults, 58 those who responded

afrmatively to the question wereconsidered to be more physically active than those who respondednegatively.

Data AnalysisIndividuals were classied as beingof normal weight, overweight, mod-erately obese, or severely obesebased on their BMI. For continuousdata, descriptive statistics are pre-sented as means and standard devia-

tions, and categorical data are pre-sented as frequencies (percentages).Mobility and balance were comparedamong weight groups using analysisof variance (ANOVA). Post hoc pair- wise comparisons were conductedfor continuous data. Chi-square analyses were conducted for categoricaldata. One-tailed tests were usedbecause there was a directionalhypothesis that mobility and balance would be poorer as BMI increased.

Multiple linear regression analysis was used to examine the associationbetween BMI and mobility and bal-ance during standing and walking while controlling for age, sex, minor-ity status, education level, physicalactivity level, and number of comor-bid conditions.

The level of signicance was set at.05. Data analyses were performed with the SAS statistical package (ver-sion 9.2).

Role of the Funding SourceThis research was funded by TheUniversity of Pittsburgh Older Amer-icans Independence Center (grantP30 AG024827). Dr Brach was sup-ported by a Paul B. Beeson Career

Development Award (K23 AG026766). Dr Studenski was sup-ported by the National Institute on Aging (grant K07 AG023641).

ResultsTable 1 provides a summary of thedemographic variables, behavioralrisk factors, fall characteristics, and

prevalent chronic conditions for allparticipants stratied by weightgroup. Of the 119 participants, 28(24%) were of normal weight(BMI 18.524.9 kg/m 2 ), 43 (36%)

were overweight (BMI 2529.9kg/m 2 ), 31 (26%) were moderately obese (BMI 3034.9 kg/m 2 ), and 17(14%) were severely obese (BMI 35kg/m 2 ). The mean age of the partic-ipants was 77.6 years (SD 5.9).There were more women (72%) inour sample than men, and most par-ticipants classied their race as white (87%). Several characteristicsof the participants were associated with higher BMI levels. Individuals with higher BMI levels were morelikely to be black or Hispanic andless likely to report walking for exer-cise compared with the normal weight group ( P .05). There wereno differences among weight groupsin the total number of comorbidhealth conditions reported. How-ever, compared with the other weight groups, those who weremoderately obese were more likely to report having lung disorders( P .005). There were no differences

in the number of falls or fear of fall-ing among weight groups.

The Figure illustrates self-reportedglobal mobility and balance ratingsstratied by weight group. Com-pared with participants who were of normal weight and those who wereoverweight, those with moderateand severe obesity were less likely toreport their mobility as very good or excellent (52%, 55%, 39%, and 6%,

respectively; P .005). There wereno differences in self-reported rat-ings of balance among weightgroups.

Table 2 provides a description of performance-based mobility and bal-ance measures stratied by weightgroup. Participants with severe obe-sity (n 17) had the lowest levels of mobility on the performance-basedmeas ures, followed by those who

SAS Institute Inc, 100 SAS Campus Dr, Cary,NC 27513-2414.

Figure.Global rating of mobility and balance as excellent or very good, stratied by weightgroup. Asterisk indicates P .005.




8/14

were moderately obese (n 31),overweight (n 42), and of normal weight (n 29). Higher BMI category was not associated with differencesin balance. For the mobility mea-sures, post hoc pair-wise compari-sons revealed that individuals who were of normal weight and those who were overweight were similar in performance; however, individu-als with obesity performed more

poorly compared with the other weight groups.

Table 3 provides the results for thepercentage of participants who wereable to complete the performance-based measures of balance. Com-pared with those who were overweight and those who were of normal weight, a trend was observed with a greater percentage of partici-

pants with moderate and severe obe-sity unable to complete the unilateralstance test ( P .10).

Table 4 provides the results for theseries of linear regressions examin-ing the association between BMI andmobility and between BMI and bal-ance during standing and walking.In unadjusted analyses (model 1),BMI was most strongly related to

mobility (gait speed, adjusted R2

.14, P .0001) and to a lesser extentrelated to balance during standing(unilateral stance test, adjusted R2

.04. P .03) and balance during walk-ing (obstacle walk test, adjusted R2 .03, P .04). After adjusting for age, sex, minority status, physicalactivity level, and total number of comorbid conditions (model 2), BMIremained signicantly related to

Table 2.Description of Performance-Based Mobility and Balance Measures Stratied by Weight Group

Measure

Normal Weight(n 29)X (SD)

Overweight(n 42)X (SD)

Moderate Obesity(n 31)X (SD)

Severe Obesity(n 17)X (SD) P

MobilityFigure-of-8 walk test (s) 9.1 (2.8) 9.3 (2.6) 11.2 (4.5) 11.4 (4.5) .02

Gait speed (m/s) 1.20 (0.2) 1.11 (0.2) 1.0 (0.3) 0.86 (0.2) .001 a

Timed Up & Go Test (s) 9.1 (3.2) 9.9 (2.6) 11.7 (4.5) 12.9 (4.9) .002 b

Six-Minute Walk Test (ft) c (n 107) 1,278.3 (276.2) 1,184.9 (266.7) 954.1 (282.5) 836.9 (389.9) .001 d

Timed chair stands (s) (n 105) 12.2 (2.7) 13.8 (4.0) 15.3 (5.4) 15.9 (6.3) .03

Balance with standing

Eyes closed, narrow stance (s) 29.2 (2.8) 29.3 (4.2) 26.2 (8.4) 28.4 (6.6) .12

Tandem stance test (s) (n 89) 22.4 (11.4) 21.3 (11.0) 21.7 (11.3) 19.4 (12.9) .89

Unilateral stance test (s) (n 97) 10.6 (9.7) 10.1 (8.8) 6.2 (7.0) 6.4 (7.9) .17

Postural responses (total no.) 3.4 (2.9) 3.5 (4.1) 3.2 (2.3) 3.6 (3.3) .96

Balance with walking

Narrow walk test (s) (n 101) 4.9 (1.6) 5.3 (2.4) 5.8 (1.9) 5.7 (1.5) .32

Narrow walk test (no. of deviations) 1.3 (2.5) 2.5 (3.8) 2.5 (2.9) 3.8 (2.9) .14

Obstacle walk test (s) 8.0 (4.5) 8.2 (3.5) 10.7 (7.8) 10.8 (4.5) .10a Difference between normal weight and moderate obesity 0.21 s, 95% condence interval (CI) 0.030.38, P .05; difference between normal weight andsevere obesity 0.34 s, 95% CI 0.130.54, P .05.b Difference between normal weight and severe obesity 3.82 s, 95% CI 0.657.0, P .05; difference between overweight and severe obesity 3.02 s, 95%CI 0.036.01, P .05.c 1 ft 0.3048 m.d Difference between normal weight and moderate obesity 324 ft, 95% CI 96553, P .05; difference between normal weight and severe obesity 441 ft,95% CI 174709, P .05; difference between overweight and moderate obesity 231 ft, 95% CI 20441, P .05; difference between overweight andsevere obesity 348 ft, 95% CI 95601, P .05.

Table 3.Percentage of Completion for Performance-Based Measures of Balance by WeightGroup

MeasureNormalWeight Overweight

ModerateObesity

SevereObesity P

Tandem stance test 79% 79% 65% 76% .42

Unilateral stance test 90% 86% 77% 64% .10

Narrow walk test 83% 93% 81% 76% .48

Obstacle walk test 90% 95% 90% 82% .60


http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/


9/14

mobility ( .015, standard error [SE] .004, P .0001). Body massindex approached having a signi-cant association with balance duringstanding ( .331, SE .189, P .08)and balance during walking ( .181,SE .093, P .06).

Discussion When examining balance and mobil-ity across weight groups incommunity-dwelling older adults,there were more differences inmobility than in balance. Individuals who were classied as being of nor-

mal weight and those classied asoverweight were similar in mobility,but individuals with moderate obe-sity and those with severe obesity demonstrated consistently lower performance than the other groups.The observed relationship betweenBMI and poor mobility suggests thatmobility in older adults is impaired atall levels of obesity.

In our study, self-report of mobility,

but not balance, was different for participants with obesity. Individuals who were of normal weight andthose who were overweight had asimilar perception of mobility. Although self-reported mobility declined for participants who weremoderately obese, those with moresevere obesity were much less likely to report mobility as very good or excellent. The nding of more fre-quent self-reported mobility limita-

tion in individuals with obesity isconsistent with the ndings of previous studies in older adults. 10,14,59 Ina study of 6,981 older men and women, LaCroix et al 14 found thatthere was a strong associationbetween loss of mobility and high BMI levels. Launer et al 10 examinedthe association between BMI andself-reported mobility disability inthe NHANES I EpidemiologicalFollow-up Study and found that BMI was related to mobility disability incommunity-dwelling older women;specically, individuals in the high

tertile for BMI had greater risk of impairment compared with those inthe low tertile for BMI.

Higher BMI levels were associated with poorer mobility on performance-based measures. Thus, our partici-pants self-reports of poor mobility were consistent with the ndings onthe performance-based measures. We found that mobility worsened with increased BMI level; however,

post hoc pair-wise comparisonsrevealed the groups with moderateand severe obesity differed from theother weight groups on most of themeasures.

In our sample, only the normal weight group achieved a desirablegait speed ( 1.2 m/s) based on aprevious study in older adults. 60 For participants who were overweightand those who wer e obese, the

mean gait speed was 1.2 m/s, which may have implications for these individuals to function success-fully in the community. For example,in order to safely negotiate through atrafc intersection, an individualmust be able to walk at a speed of 1.2m/s. 61 Furthermore, the gait speedsfound in the participants classied asmoderately or severely obese (1.0and 0.86 m/s) are not just indicativeof impaired functioning, but alsohave been found to be associated with higher risk for adverse health events, including nursing home

admission, falls, and disability. 60,62These ndings underscore the detri-mental impact that excess weighthas on mobility in older adults, evenin those with less severe obesity.

Higher BMI levels were not associ-ated with poorer performance onmeasures of balance during standing, which is consistent with partici-pants self-reported balance. Thisnding was not surprising given that

there were no differences in fall his-tory among the weight groups; how-ever, our ndings differ from thoseof previous studies that demon-strated more postural instability 38and greater risk of falls in individuals with obesity. 63 Although increasedBMI in older adults may inuencebalance, other factors associated with aging also may contribute topostural instability. These factorsinclu de sarcopenia , dened as the

Table 4.Relationship Between Body Mass Index (BMI) and Mobility and Between BMI and Balance During Standing and Walking

Measure

Gait Speed Unilateral Stance Test Obstacle Walk Test

Model 1 a Model 2 b Model 1 Model 2 Model 1 Model 2

BMI, (SE)c 0.02 (0.004) d 0.015 (0.004) d 0.39 (0.173) e 0.33 (0.189) 0.20 (0.099) e 0.18 (0.093)

Adjusted R2 .14 .41 .04 .13 .03 .20

Model P value .0001 .0001 .03 .004 .04 .0001a Unadjusted linear regression.b Linear regressions adjusted for age, sex, minority status, education level, physical activity level, and total number of comorbid conditions.c SE standard error.d P .001.e P .05.


http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/


10/14

age-related loss of skeletal musclemass and strength (force-generatingcapacity) 64 ; changes in body fat dis-tribution, specically an increase in visceral abdominal fat and a decrease

in subcutaneous fat65

; and a declinein the quality of skeletal muscle. 66 Itis plausible that changes in skeletalmuscle and body fat distribution may be related more to postural instabil-ity than to BMI alone, which may explain the lack of a stronger rela-tionship between balance and BMI inthe current study.

Although not statistically signicant,differences in static balance among weight groups may be clinical mean-ingful. For example, individuals who were of normal weight and those who were overweight had similar performance on the unilateral stancetest (10.6 and 10.1 seconds, respec-tively) compared with individuals with moderate obesity and those with severe obesity, who had poorer performance on the unilateral stancetest (6.2 and 6.4 seconds, respec-tively). A previous study of falls inolder adults who were obese

showed no difference in perfor-mance on standing balance tests inindividuals with obesity compared with those of normal weight; how-ever, in contrast to our study, individuals with obesity reported ahigher prevalence of falls. 63 Interest-ingly, all measures of balance werestatic, and no measures of balanceduring walking were included. Fur-ther investigation of the impact of obesity on balance in older adults is

warranted and should take intoaccount skeletal muscle mass,strength, and body fat distribution.

A greater number of individuals with moderate obesity and severe obesity were unable to complete theperformance-based measures of bal-ance compared with those who were of normal weight and those who were overweight. Lack of com-pletion of balance measures in par-

ticipants with higher BMI wasrelated to inability to assume the testpositions (eg, tandem stance) anddifculty performing certain move-ments (eg, narrow walk test). Thus,

had all participants with obesity been able to complete the balancemeasures, our results may have dif-fered. These ndings reinforce theneed for the identication of balancemeasures most appropriate for use inindividuals with higher BMIs, specif-ically those that incorporate balanceduring dynamic activities and thosethat allow individuals with differingbody sizes to assume the positionrequired for the test.

Obesity is associated with increasedburden of chronic disease anddecreased physical activity level,both of which have been shown tonegatively affect mobility. 14,67,68 Inthe current study, individuals with obesity were more likely to havelung disorders and were less likely toengage in physical activity compared with those who were overweightand those of normal weight. Theassociation between BMI and mobil-

ity was partially explained by thesefactors; however, the data suggestthat even after adjusting for many potential confounding factors, BMIstill was independently related tomobility.

The recommendation for weight lossin older adults is controversialbecause there is a risk of acceleratingthe age-related decline in lean massand bone density, thereby leading to

poorer physical function.69,70

How-ever, interventions that facilitate weight loss through diet and exer-cise have been shown to improvemobility, balance, and health-relatedquality of life in older adults. 31,7173 Villareal et al 8 suggested that weightloss programs for older adultsinclude strategies to minimize mus-cle and bone loss and should includethe adoption of resistance exerciseand regular physical activity. This

recommendation should be takeninto account by physical therapists who are frequently involved in exer-cise prescription for older adults with obesity.

There are several limitations to thecurrent study. First, the results of thestudy may not apply to the generalcommunity-dwelling older popula-tion because our sample was a vol-unteer sample of predominantly white women. Furthermore, there were unequal numbers of partici-pants in each weight group, and notall participants were able to com-plete the physical performance tests.Individuals in the moderately andseverely obese categories had thelowest completion rates compared with those in the normal weight or overweight categories. Our resultsmight have differed had there beenequal numbers of participants in the weight groups and had completionrates been higher across the weightgroups. Several testers were respon-sible for data collection in this study, which could have inuenced the dif-ferences among the weight groups.

However, we believe this potentiallimitation is unlikely in that partici-pant assignment to testers was com-pletely random and all testers evalu-ated participants from each of theBMI groupings. In addition, although not established in our study, theinterrater reliability of many of themeasures that we used has beenestablished in other studies and isquite good.

An additional limitation of the cur-rent study was the use of the BMI asan indicator of body size. Older individuals typically have less lean massand more fat mass than younger adults, and as a result, the BMI may underestimate body fat in theseindividuals. 74 Furthermore, there isdebate about whether the fat redis-tribution and relative loss of fat-freemass that occur with aging may exer t more inuence than the BMI in


http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/http://ptjournal.apta.org/


11/14

determining health risks associated with obesity in older adults. 75 Moresophisticated measures of total body fat are available, including dual-energy x-ray absorptiometry (DXA)

and electron beam computed tomog-raphy (EBT). Even so, prior research has shown a strong relationshipbetween BMI and total body fatdetermined by EBT in older women( r .89, P .0001), suggesting thatBMI may be an acceptable initialscreening tool in the clinical set-ting. 76 In addition, DXA and EBT may not be practical measures of totalbody fat in the clinical settingbecause these tests are more time-consuming, require more complextraining, and are expensive to use. We recognize the limitations of theBMI; however, in the absence of amore suitable measure, the use of the BMI may provide an opportunity for physical therapists to incorporatehealth promotion into clinical prac-tice. When utilizing the BMI, careshould be taken to interpret resultsalong with assessment of regional fatdistribution as well as visual inspec-tion of fat and muscle mass to

decrease risk of misclassication of body size.

ConclusionThis study used a comprehensivebattery of self-report andperformance-based measures tocharacterize mobility and balance inolder adults who were of normal weight, overweight, moderately obese, and severely obese. Higher BMI levels were associated with

poorer mobility but not balance. Fur-thermore, individuals classied asbeing of normal weight and thoseclassied as overweight were similar in mobility, whereas individuals with obesity had greater impairments inmobility. Although those partici-pants with severe obesity (BMI 35kg/m 2 ) were most impaired, older adults with less severe obesity (BMI 3034.9 kg/m 2 ) also demon-strated signicant decrements in

mobility. Body mass index should beconsidered when selecting measuresof mobility and balance becauseolder adults with obesity may beunable to achieve the position for

some tests. When treating older adults with obesity, physical thera-pists are in a unique position to pre-scribe exercise to address associatedmedical complications as well as thefunctional consequences of obesity.

Dr Hergenroeder and Dr Brach providedconcept/idea/research design and data analysis. All authors provided writing. Mr Wert,Dr Hile, and Dr Brach provided project man-agement. Dr Studenski and Dr Brach pro-vided fund procurement and facilities/equip-

ment. Dr Brach provided participants. Mr Wert and Dr Studenski provided consulta-tion (including review of manuscript beforesubmission).

This study was approved by the InstitutionalReview Board of the University of Pittsburgh.

This work was presented on at Physical Ther-apy 2009: APTAs Annual Conference &Exposition; June 12, 2009; Baltimore,Maryland.

This research was funded by The Universityof Pittsburgh Older Americans Indepen-dence Center (grant P30 AG024827). Dr

Brach was supported by a Paul B. BeesonCareer Development Award (K23 AG026766). Dr Studenski was supported bythe National Institute on Aging (grant K07 AG023641).

DOI: 10.2522/ptj.20100214

References1 Mendez MA, Monteiro CA, Popkin BM.

Overweight exceeds underweight among women in most developing countries. Am J Clin Nutr . 2005;81:714721.

2 Hedley AA, Ogden CL, Johnson CL, et al.Prevalence of overweight and obesity

among US children, adolescents, andadults, 19992002. JAMA. 2004;291:28472850.

3 Ogden CL, Carroll MD, Curtin LR, et al.Prevalence of overweight and obesity inthe United States, 19992004. JAMA.2006;295:15491555.

4 Kopelman PG. Obesity as a medical prob-lem. Nature . 2000;404:635643.

5 Pi-Sunyer FX. Medical hazards of obesity. Ann Intern Med . 1993;119(7 pt 2):655660.

6 Colditz GA. Economic costs of obesity andinactivity. Med Sci Sports Exerc . 1999;31(11 suppl):S663S667.

7 Finkelstein EA, Fiebelkorn IC, Wang G.National medical spending attributable tooverweight and obesity: how much, and whos paying? Health Aff (Millwood) .2003. Suppl Web Exclusives:W321926.

8 Villareal DT, Apovian DT, Kushner RF.Obesity in older adults: technical review

and position statement of the AmericanSociety for Nutrition and NAASO, TheObesity Society. Obes Res . 2005;13:18491863.

9 Han TS, Tijhuis MA, Lean ME, Seidell JC.Quality of life in relation to overweightand body fat distribution. Am J Public Health . 1998;88:18141820.

10 Launer LJ, Harris T, Rumpel C, Madans J.Body mass index, weight change, and risk of mobility disability in middle-agedand older women: the epidemiologicfollow-up study of NHANES I. JAMA. 1994;271:10931098.

11 Apovian CM, Frey CM, Wood GC, et al.Body mass index and physical function inolder women. Obes Res. 2002;10:740747.

12 Himes CL. Obesity, disease, and functionallimitation in later life. Demography . 2000;37:7382.

13 Jensen GL, Friedmann JM. Obesity is asso-ciated with functional decline incommunity-dwelling rural older persons.

J Am Geriatr Soc . 2002;50:918923.14 LaCroix AZ, Guralnik JM, Berkman LF,

et al. Maintaining mobility in late life; II:smoking, alcohol consumption, physicalactivity, and body mass index. Am J Epi- demiol . 1993;137:858869.

15 Stenholm S, Rantanen T, Alanen E, et al.Obesity history as a predictor of walkinglimitation at old age. Obesity (Silver Spring) . 2007;15:929938.

16 Blaum CS, Xue QL, Michelon E. The asso-ciation between obesity and the frailty syn-drome in older women: the WomensHealth and Aging Studies. J Am Geriatr Soc . 2005;53:927934.

17 Mendes de Leon CF, Guralnik JM,Bandeen-Roche K. Short-term change inphysical function and disability: the Wom-ens Health and Aging Study. J Gerontol B Psychol Sci Soc Sci . 2002;57:S355S365.

18 Guralnik JM, Simonsick EM. Physical dis-ability in older Americans. J Gerontol .1993;48 Spec. No.:310.

19 Alley DE, Chang VW. The changing rela-tionship of obesity and disability, 19882004. JAMA. 2007;298:20202027.

20 Garrow JS, Webster J. Quetelets index(W/H2) as a measure of fatness. Int J Obes .1985;9:147153.

21 Physical status: The Use and Interpreta- tion of Anthropometry . Geneva, Switzer-land: World Health Organization; 1995. WHO Technical Report Series 854.

22 Clinical guidelines on the identication,evaluation, and treatment of overweightand obesity in adults: executive summary;Expert Panel on the Identication, Evalu-ation, and Treatment of Overweight in Adults. Am J Clin Nutr . 1998;68:899917.




12/14

23 Baumgartner RN, Heymseld SB, Roche AF. Human body composition and the epi-demiology of chronic disease. Obes Res .1995;3:7395.

24 Blew RM, Sardinha LB, Milliken LA, et al. Assessing the validity of body mass indexstandards in early postmenopausal wom-

en. Obes Res . 2002;10:799 808.25 Evans EM, Rowe DA, Racette SB, et al. Isthe current BMI obesity classicationappropriate for black and white post-menopausal women? Int J Obes (Lond) .2006;30:837843.

26 Seidell JC, Kahn HS, Williamson DF, et al.Report from a Centers for Disease Controland Prevention workshop on use of adultanthropometry for public health and pri-mary health care. Am J Clin Nutr . 2001;73:123126.

27 Nelson ME, Rejeski W, Blair SN, et al. Phys-ical activity and public health in older adults: recommendation from the Ameri-can College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc . 2007;39:14351445.

28 Haskell WL, Lee IM, Pate RR, et al. Physicalactivity and public health: updated recom-mendation for adults from the AmericanCollege of Sports Medicine and the Amer-ican Heart Association. Med Sci Sports Exerc . 2007;39:14231434.

29 Jakicic JM, Clark K, Coleman E, et al. American College of Sports Medicine posi-tion stand: appropriate intervention strat-egies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc . 2001;33:21452156.

30 Saris WH, Blair SN, van Baak M, et al. How much physical activity is enough to pre- vent unhealthy weight gain: outcome of the IASO 1st Stock Conference and con-sensus statement. Obes Rev . 2003;4:101114.

31 Villareal DT, Banks M, Sinacore DR, et al.Effect of weight loss and exercise onfrailty in obese older adults. Arch Intern Med . 2006;166:860866.

32 Johnson NA, Sachinwalla T, Walton DW,et al. Aerobic exercise training reduceshepatic and visceral lipids in obese individuals without weight loss. Hepatology .2009;50:11051112.

33 Ross R, Bradshaw AJ. The future of obesity reduction: beyond weight loss. Nat Rev Endocrinol . 2009;5:319325.

34 Dekker MJ, Lee S, Hudson R, et al. An exer-cise intervention without weight lossdecreases circulating interleukin-6 in lean

and obese men with and without type 2diabetes mellitus. Metabolism . 2007;56:332338.

35 Sack S, Radler DR, Mairella KK, et al. Phys-ical therapists attitudes, knowledge, andpractice approaches regarding people who are obese. Phys Ther . 2009;89:804815.

36 Browning RC, Baker EA, Herron JA, KramR. Effects of obesity and sex on the ener-getic cost and preferred speed of walking.

J Appl Physiol . 2006;100:390398.37 de Souza SA, Faintuch J, Valezi AC, et al.

Gait cinematic analysis in morbidly obesepatients. Obes Surg . 2005;15:12381242.

38 Corbeil P, Simoneau M, Rancourt D, et al.Increased risk for falling associated with obesity: mathematical modeling of pos-tural control. IEEE Trans Neural Syst Rehabil Eng . 2001;9:126 136.

39 Kuczmarski RJ, Carroll MD, Flegal KM,Trojano RP. Varying body mass index cut-

off points to describe overweight preva-lence among U.S. adults: NHANES III(1988 to 1994). Obes Res . 1997;5:542548.

40 Andreyeva T, Sturm R, Ringel JS. Moderateand severe obesity have large differencesin health care costs. Obes Res . 2004;12:19361943.

41 Hess RJ, Brach JS, Piva SR, Van Swearingen JM. Walking skill can be assessed in older adults: validity of the Figure-of-8 Walk Test. Phys Ther . 2010;90:8999.

42 Van Swearingen JM, Brach JS, Hess RJ,et al. Clinical correlates of motor controlin walking; the Figure-of-8 Walk Test.Paper presented at: 59th Annual ScienticMeeting of the Gerontological Society of America; November 1620, 2006; Dallas,Texas.

43 Steffen T, Seney M. Test-retest reliability and minimal detectable change on balanceand ambulation tests, the 36-item short-form health survey, and the unied Parkin-son disease rating scale in people with parkinsonism [erratum in: Phys Ther .2010;90:462]. Phys Ther . 2008;88:733746.

44 Bohannon RW. Comfortable and maxi-mum walking speed of adults aged 2079 years: reference values and determinants. Age Ageing . 1997;26:1519.

45 Brach JS, Perera S, Studenski SA, Newman AB. The reliability and validity of measuresof gait variability in community-dwellingolder adults. Arch Phys Med Rehabil .2008;89:22932296.

46 Walsh JP. Foot fall measurement technol-ogy. In: Craik RL, Oatis CA, eds. Gait Anal- ysis: Theory and Application . 1995:125142.

47 Nordin E, Rosendahl E, Lundin-Olsson L.Timed Up & Go Test: reliability in older people dependent in activities of daily liv-ing: focus on cognitive state. Phys Ther .2006;86:646655.

48 Podsiadlo D, Richardson S. The timed Up& Go: a test of basic functional mobility for frail elderly persons. J Am Geriatr Soc .1991;39:142148.

49 King MB, Judge JO, Whipple R, Wolfson L.Reliability and responsiveness of two

physical performance measures examinedin the context of a functional trainingintervention. Phys Ther . 2000;80:816.

50 Curb JD, Ceria-Ulep CD, Rodriguez BL,et al. Performance-based measures of physical function for high-function popu-lations. J Am Geriatr Soc . 2006;54:737742.

51 Cornoni-Huntley J, Ostfeld AM, Taylor JO,et al. Established Populations for Epidemi-ologic Studies of the Elderly: study designand methodology. Aging (Milano) . 1993;5:2737.

52 Studenski SA, Perera S, Wallace D, et al.Physical performance measures in the clin-ical setting. J Am Geriatr Soc . 2003;51:314322.

53 Chandler JM, Duncan PW, Studenski SA.Balance performance on the posturalstress test: comparison of young adults,

healthy elderly, and fallers. Phys Ther .1990;70:410415.54 Bandinelli S, Pozzi M, Lauretani F, et al.

Adding challenge to performance-basedtests of walking: the Walking InCHIANTIToolkit (WIT). Am J Phys Med Rehabil .2006;85:986991.

55 Simonsick EM, Newman AB, Nevitt MC,et al. Measuring higher level physical func-tion in well-functioning older adults:expanding familiar approaches in theHealth ABC Study. J Gerontol A Biol Sci Med Sci . 2001;56:M644M649.

56 Rigler SK, Studenski SA, Wallace D, et al.Co-morbidity adjustment for functionaloutcomes in community-dwelling older adults. Clin Rehabil . 2002;16:420 428.

57 Lachman ME, Howland J, Tennstedt S,et al. Fear of falling and activity restriction:the Survey of Activities and Fear of Fallingin the Elderly (SAFE). J Gerontol B Psychol Sci Soc Sci . 1998;53:P43P50.

58 Eyler AA, Brownson RC, Bacak SJ, House-mann RA. The epidemiology of walkingfor physical activity in the United States. Med Sci Sports Exerc . 2003;35:15291536.

59 Galanos AN, Pieper CF, Cornoni-Huntley JC, et al. Nutrition and function: is there arelationship between body mass indexand the functional capabilities of community-dwelling elderly? J Am Geriatr Soc . 1994;42:368373.

60 Cesari M, Kritchevsky SB, Penninx BW,et al. Prognostic value of usual gait speedin well-functioning older people: resultsfrom the Health, Aging and Body Compo-sition Study. J Am Geriatr Soc . 2005;53:16751680.

61 Langlois JA, Keyl PM, Guralnik JM, et al.Characteristics of older pedestrians whohave difculty crossing the street. Am J Public Health . 1997;87:393397.

62 Guralnik JM, Ferrucci L, Simonsick EM,et al. Lower-extremity function in personsover the age of 70 years as a predictor of subsequent disability. N Engl J Med . 1995;332:556561.

63 Fjeldstad C, Fieldstad AS, Acree LS, et al.The inuence of obesity on falls and qual-ity of life. Dyn Med . 2008;7:4.

64 Lord SR, Ward JA, Williams P, Anstey KJ. Physiological factors associated with falls in older community-dwelling women.

J Am Geriatr Soc . 1994;42:11101117.65 Ochi M, Tabara Y, Kido T, et al. Quadri-

ceps sarcopenia and visceral obesity arerisk factors for postural instability in themiddle-aged to elderly population. Geriatr Gerontol Int . 2010;10:233243.

66 Goodpaster BH, Park SW, Harris TB, et al.The loss of skeletal muscle strength,mass, and quality in older adults: thehealth, aging and body composition study.

J Gerontol A Biol Sci Med Sci . 2006;61:10591064.




13/14

67 Koster A, Penninx BW, Newman AB, et al.Lifestyle factors and incident mobility lim-itation in obese and non-obese older adults. Obesity (Silver Spring) . 2007;15:31223132.

68 Brach JS, Van Swearingen JM, FitzGeraldSJ, et al. The relationship among physical

activity, obesity, and physical function incommunity-dwelling older women. Prev Med . 2004;39:7480.

69 Roubenoff R. Sarcopenia: effects on body composition and function. J Gerontol A Biol Sci Med Sci . 2003;58:10121017.

70 Jensen LB, Quaade F, Sorensen OH. Boneloss accompanying voluntary weight lossin obese humans. J Bone Miner Res . 1994;9:459463.

71 Messier SP, Loeser RF, Mitchell MN, et al.Exercise and weight loss in obese older adults with knee osteoarthritis: a prelimi-nary study. J Am Geriatr Soc . 2000;48:10621072.

72 Christensen R, Bartels EM, Astrup A, Blid-dal H. Effect of weight reduction in obese

patients diagnosed with knee osteoarthri-tis: a systematic review and meta-analysis. Ann Rheum Dis . 2007;66:433439.

73 Messier SP, Loeser RF, Miller GD, et al.Exercise and dietary weight loss in overweight and obese older adults with kneeosteoarthritis: the Arthritis, Diet, and Activity Promotion Trial. Arthritis Rheum .2004;50:15011510.

74 Borkan GA, Hults DE, Gerzof SG, et al. Agechanges in body composition revealed by computed tomography. J Gerontol . 1983;38:673677.

75 Zamboni M, Mazzali G, Zoico E, et al.Health consequences of obesity in theelderly: a review of four unresolved ques-

tions. Int J Obes (Lond) . 2005;29:10111029.76 Storti KL, Brach JS, FitzGerald SJ, et al.

Relationships among body compositionmeasures in community-dwelling older women. Obesity (Silver Spring) . 2006;14:244251.




14/14

doi: 10.2522/ptj.20100214Originally published online June 16, 2011

2011; 91:1223-1234.PHYS THER.Hile, Stephanie A. Studenski and Jennifer S. BrachAndrea L. Hergenroeder, David M. Wert, Elizabeth S.Mobilityand Performance-Based Measures of Balance andAssociation of Body Mass Index With Self-Report

References

http://ptjournal.apta.org/content/91/8/1223#BIBLfor free at:This article cites 72 articles, 17 of which you can access

Cited by

http://ptjournal.apta.org/content/91/8/1223#otherarticles

This article has been cited by 1 HighWire-hosted articles:

InformationSubscription http://ptjournal.apta.org/subscriptions/

Permissions and Reprints http://ptjournal.apta.org/site/misc/terms.xhtml

Information for Authors http://ptjournal.apta.org/site/misc/ifora.xhtml
http://ptjournal.apta.org/content/91/8/1223#BIBLhttp://ptjournal.apta.org/content/91/8/1223#BIBLhttp://ptjournal.apta.org/content/91/8/1223#BIBLhttp://ptjournal.apta.org/content/91/8/1223#otherarticleshttp://ptjournal.apta.org/subscriptions/http://ptjournal.apta.org/site/misc/terms.xhtmlhttp://ptjournal.apta.org/site/misc/ifora.xhtmlhttp://ptjournal.apta.org/http://ptjournal.apta.org/site/misc/ifora.xhtmlhttp://ptjournal.apta.org/site/misc/terms.xhtmlhttp://ptjournal.apta.org/subscriptions/http://ptjournal.apta.org/content/91/8/1223#otherarticleshttp://ptjournal.apta.org/content/91/8/1223#BIBL

Documents

PHYS THER 2011 Hergenroeder 1223 34