Predictors of falls in women

582 | september 2010 | volume 40 | number 9 | journal of orthopaedic & sports physical therapy

[ research report ]

status.8 The consequences range from mi-nor injuries19 to more severe conditions such as fractures.23 Falls are responsible for about 90% of hip fractures in the el-

1 Professor of Physical Education, Department of Obstetrics and Gynecology, School of Medicine, Unicamp, Campinas, São Paulo, Brazil. 2 Associate Professor, Department of Obstetrics and Gynecology, School of Medicine, Unicamp, Campinas, São Paulo, Brazil. 3 Statistics, Department of Obstetrics and Gynecology, School of Medicine, Unicamp, Campinas, São Paulo, Brazil. 4 Assistant Professor, Department of Otolaryngology, School of Medicine, Unicamp, Campinas, São Paulo, Brazil. 5 Physiotherapist, Department of Obstetrics and Gynecology, School of Medicine, Unicamp, Campinas, São Paulo, Brazil. 6 Associate Professor, Department of Obstetrics and Gynecology, School of Medicine, Unicamp, Campinas, São Paulo, Brazil. Financial support for this study was provided by the Foundation for Research Support of the State of São Paulo and the Coordination for the Improvement of Higher Level Personnel Research grant for doctorate degree. The protocol for this study was approved by The Committee of Ethics of School of Medicine, Unicamp, Campinas, São Paulo, Brazil. Address correspondence to Dr Lúcia Costa-Paiva, Rua Alexandre Fleming, 101-Cidade Universitária Zeferino Vaz Barão Geraldo, Campinas, São Paulo, Brazil, Maibox 6081, 13083-881. E-mail: [email protected]

Raimunda BeseRRa da silva, PhD1 • Lúcia costa-Paiva, MD, PhD2 • sirLei siani Morais, MS3 Raquel mezzaliRa, MD, MS4 • néviLLe de oLiveira Ferreira, PT, MS5 • aarão Mendes Pinto-neto, MD, PhD6

Predictors of Falls in Women With and Without Osteoporosis

derly6 and are associated with increased morbidity and mortality rates. Research in some Latin American cities has shown that mortality rates due to hip fractures

osteoporosis and falls are common problems in the elderly. In developed countries, between 21% and 38% of individuals who are 65 years or older report a history of 1 or more falls per year,2,24 affecting mainly women over 70 years.9 Falls are a risk

factor for fractures.21 Falls are multifactorial in nature, resulting from a combination of extrinsic factors related to the individual’s environment and intrinsic factors related to the individual’s physical and cognitive

t stUdY desiGn: Cross-sectional study.

t oBJective: To evaluate the relationship be-tween the occurrence of falls and muscle strength, flexibility, and balance in postmenopausal women with and without osteoporosis.

t BacKGroUnd: Osteoporosis and falls are common problems encountered in the elderly.

t MetHods: A total of 133 women with and 133 without osteoporosis, aged 60 years or greater, were included in the study. Women were interviewed about clinical and social demographic characteristics and the occurrence of falls in the previous 12 months. The variables evaluated were presence of osteoporosis, muscle strength, flex-ibility, and balance.

t resULts: A significantly higher percentage of women with osteoporosis (51%) compared to those without osteoporosis (29%) had a history of at least 1 fall within the previous 12 months. There

was a significant and inverse association between trunk extension strength and trunk flexion range of motion with falls. Logistic regression analyses showed that the variables associated with falls were trunk extension strength and presence of osteoporosis. Greater trunk extension strength was associated with a lower risk for falls (odds ratio, 0.97), while the presence of osteoporosis increased fall risk by a factor of 2.17.

t concLUsions: A greater percentage of women with postmenopausal osteoporosis had a history of 1 or more falls within the previous year and a higher risk of recurrent falls than women without osteoporosis. Muscle strength of the lumbar spine and the presence of osteoporosis are intrinsic factors associated with the risk of falls. J Orthop Sports Phys Ther 2010;40(9):582-588. doi:10.2519/jospt.2010.3239

t KeY Words: balance, bone density, flexibility, muscle strength, postmenopausal

range from 23.2% to 30.5%.18

The following intrinsic factors are as-sociated with increased risk of falls: being of female sex, decreased physical mobil-ity, depression,9 advanced age, diabetes, hearing disorders,2 impairment in body balance,24 impaired muscle strength22 and vision, osteoarticular disease, and the use of medication.8 Some intrin-sic factors, such as sex and age, are not modifiable, while others, such as muscle strength,7 flexibility,27 and body balance,34 are potentially modifiable based on ad-equate intervention. To be successful in preventing fractures,10,21 in addition to interventions related to optimize bone mineral density,20 it is also necessary to focus interventions on factors that pre-dispose individuals to falls.21,30

Few studies concerning potential risk factors for falls in women with osteoporo-sis have been conducted. This population may have intrinsic factors that increase their risk for falls compared to peers. In theory, changes in body balance,15 pos-ture, and muscle strength26 may be af-fected by the presence of osteoporosis and therefore may increase the risk for falls. The identification of risk factors in-trinsic to falls and interventions appro-priate for these factors may decrease the incidence of fractures in postmenopausal women with osteoporosis.

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journal of orthopaedic & sports physical therapy | volume 40 | number 9 | september 2010 | 583

falls and balance measure. Arnold et al1 correlated the number of falls with in-trinsic risk factors in postmenopausal women with osteoporosis. Based on a correlation value of 0.27, considering a significance level of 5% and type II er-ror of 20% (power of 80%), the neces-sary sample size was calculated at n = 40. Given a 30% rate of 1 or more falls per year, the estimated required sample size was 133 women with osteoporosis and 133 without osteoporosis.

ProceduresAll women were interviewed by the re-searcher, who collected demographic and clinical information such as age (provided by the patient), body mass index (BMI), time since menopause, ethnicity (Cauca-sian and non-Caucasian), marital status (with or without partner), occupation, smoking cigarettes (number of years), physical exercise (at least 30 minutes for 3 or more times per week), and use of medication and hormone therapy. Falls were determined during the interview when the subject reported the occur-rence, number, and location of falls in the previous 12 months. A fall was defined as an unexpected and unintentional change in position causing an individual to land

at a lower level and not resulting from sudden onset of paralysis, epileptic sei-zures, or overwhelming external force.32

Height and weight were taken during the data collection using anthropometric and stadiometer scale with the patient in standing, wearing light clothes, and barefoot.33

Evaluation of bone mass was per-formed at the Division of Nuclear Medicine at the Clinical Hospital of the Universidade Estadual de Campinas, by bone densitometry with a Lunar DPX densitometer (GE Medical Systems Lu-nar, Madison, WI). The women were placed in a supine position, with hips and knees flexed 60° to 90°. The bone density of the lumbar spine (L1-L4) was measured in the anteroposterior plane. The diagnosis of osteoporosis was based on the World Health Organization den-sitometry criteria,34 which classifies normal bone mass as a t score higher or equivalent to –1.0 SD (young adult) in the lumbar spine (L1-L4) and osteoporosis as a value lower than or equal to –2.5 SD (young adult), as measured by dual en-ergy X-ray absorptiometry (DXA).

Muscle strength of the trunk and lower limbs was evaluated by using a Crown dynamometer (range, 1-200 kg).

Research examining the association between risk factors of falls and mus-culoskeletal variables has used subjec-tive evaluation methods (like functional mobility) and has studied women aged 65 and older.15,26 Neither associations between objective musculoskeletal vari-ables and risk factors nor younger women have been studied.

The aim of this study was to evaluate the association between the occurrence of falls and muscle strength, flexibility, and static balance in postmenopausal women with and without osteoporosis.

MetHods

subjects

a cross-sectional study of 266 postmenopausal women was con-ducted, with follow-up in the

Menopause Outpatient Facility of the Women’s Integral Healthcare Center at the Universidade Estadual de Campinas. The women were selected consecutively during a routine visit for consultation for perimenopause and postmenopause problems and divided into 2 groups ac-cording to bone densitometry (133 wom-en with postmenopausal osteoporosis and 133 without osteoporosis).

Eligibility criteria included age great-er than 60 years, amenorrhea for at least 12 months, and normal bone densitom-etry or presence of osteoporosis. Women who reported musculoskeletal disease with lower limb deformity, neurologic disease with impaired balance, dizziness, tinnitus, hypoacusis and feeling of full-ness in the ear, history of malignancy, vi-sual impairments, uncontrolled diabetes mellitus, postural hypotension, uncon-trolled thyroid disorders, and medica-tion use that alter static balance were excluded from the study. The study was approved by The Research Ethics Com-mittee of the School of Medicine/Uni-versidade Estadual de Campinas and all participants provided written informed consent.

Sample size calculations were based on correlations between the number of

FiGUre 1. (A) Lumbar spine extension strength assessment. (B) Lower extremity strength assessment.


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[ research report ]

To assess trunk extension strength, the standing position with lower extremities extended was used (FiGUre 1a). To evalu-ate lower-limb strength, the standing po-sition with lower extremities flexed was used (FiGUre 1B). After positioning, the subject was asked to exert a maximum lifting force. Subjects were encouraged to produce the maximum force possible within their physical limits. The test was performed once, similar to the protocol used for the validation study.12 Measure-ments were taken after orientation and practice trials (variable to each subject) to ensure that the patients understood the test procedures.

To evaluate lumbar spine flexibility, flexion and extension of the trunk were measured by a Sanny Fleximeter device graded in degrees. The standing posi-tion was adopted by the participant with lower limbs together and extended. The measuring device was placed along the lateral trunk. Spinal flexion was evaluat-ed by asking the subject to maximally flex the trunk bringing arms toward the feet until the lower limbs tended to flex (FiG-

uRe 2a). Spinal extension was measured by requesting maximal trunk backward bending, with arms along the body, un-

til the hips projected forward (FiGUre 2B). The test was performed once, similar to the validation study.5 Measurements were taken after orientation and practice tri-als to ensure that the subjects understood the test procedures.

Static balance was assessed by stabi-lometry, which quantifies body sway. The AccuSway Plus force platform system re-corded center-of-pressure movements in the anterior-posterior (y) and lateral (x) directions, based on the forces exerted on the platform by the soles of the feet (FiGUre 3a). Assessment was performed with the subject standing barefoot on the platform with heels 2 cm apart, forming a 30° angle (FiGUre 3B). Arms were held at the sides. The subject stood still and fo-cused on a target located directly ahead, with eyes open for 30 seconds, followed by 30 seconds of testing with eyes closed. The stabilometer parameters analyzed were the mean amplitude of center-of-pressure movements in the anterior-posterior (y) and lateral (x) directions, ellipse area of center-of-pressure move-ment (anterior-posterior, lateral), and the mean velocity, with eyes opened and closed. The test was performed once, similar to the validation study.29

statistical analysisFor statistical analysis, the Mann-Whitney test was used to compare control variables among the groups. Because there were significant differences in these variables, strength, flexibility, and balance (depen-dent variables) were compared by using general linear model methodology, con-trolled by age, BMI, school education, time since amenorrhea, and physical exercise (considered as independent variables). However, because the dependent variables did not have a normal distribution, BOX-COX4 (a statistical test) was used to trans-form data into normal distribution and apply a general linear model. The control variables were not transformed. The gen-eral linear model procedure is used to test the difference in means, controlling for the variables that differed between the groups with and without osteoporosis.

To correlate strength measures, flexibil-ity, and balance with the number of falls, Spearman’s correlation coefficient and Spearman’s partial correlation coefficient (adjusted) were adjusted for age, BMI, educational level, time since menopause, physical exercise, and osteoporosis. We evaluated the variables associated with falls

FiGUre 3. (A) AccuSway Plus force platform and computer. (B) Subject standing on the platform with heels 2 cm apart and feet forming a 30° angle.

FiGUre 2. Range-of-motion assessment for lumbar flexion (A) and extension (B).


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(young adult) of the lumbar spine (L1-L4) was –2.9 0.4 in the group with osteo-porosis and 0.0 0.9 in the group with-out osteoporosis.

The majority of women in the study were white (80.5% with osteoporo-sis and 84.2% without osteoporosis), had a sedentary lifestyle (76.7% with osteoporosis and 72.9% without os-teoporosis), received hormone therapy (approximately 75% with osteoporosis), and used some type of medication for chronic diseases (approximately 90% with osteoporosis). The mean number of drugs used by women in both groups was 3 (90.2% and 85.7% in the groups with and without osteoporosis, respec-tively). The most widely used drugs were captopril, hydrochlorothiazide, and calcium. Fifty-one percent of the women with osteoporosis had a history of 1 or more falls within the previous year, compared to 29% of the women without osteoporosis (P.01). Among

by dichotomizing subjects into groups who had at least 1 fall and those with no falls. The estimated risks for falls were calculated by odds ratio (OR) (95% confidence inter-val [CI]) through binary logistic regression. The variables with significant differences among the groups were studied through bivariate analysis. Age, BMI, time since menopause, physical exercise, ethnicity, marital status, occupation, smoking, use of medication, hormone therapy, osteoporo-sis, muscle strength, flexibility and balance were examined and selected according to significance through binary logistic regres-sion with stepwise selection. For these pro-cedures, SAS Version 9.1.3 was used.

resULts

taBLe 1 shows the clinical character-istics of the women in each of the 2 groups. Women with osteopo-

rosis had a lower BMI and younger age at menopause. The mean SD t Score

those who fell during the previous year, 57% of the women with osteoporosis had recurrent falls (2 or more falls), compared to 26% for the women with-out osteoporosis (P.01).

Lumbar spine extension and lower-limb strength were lower in the group with osteoporosis. However, there was a significant difference only for muscle strength of the lower limbs (P.02). Flexibility measures found trunk exten-sion to be significantly higher (P.01) in the osteoporotic group (taBLe 2).

The comparison between balance parameters using stabilometry among the groups of women with and without osteoporosis in the test performed with the eyes open showed that women with osteoporosis had increased sway (greater amplitude) in the anterior-posterior axis compared to women in the control group. No statistically significant difference was observed in lateral sway, mean velocity of movement, and ellipse area in the tests with eyes open and closed, and in sway amplitude in the anterior-posterior di-rection with eyes closed.

Adjusted correlation analysis between intrinsic factors and falls showed very weak and inverse correlation between strength of the lumbar spine (P.03) and flexion of the spine (P.04). There were no significant correlations with any of the sway parameters evaluated (taBLe 3).

The OR for falls was calculated af-ter adjusting through multiple logistic regression for the variables found to be significant in the bivariate analysis. The independent variables entered into the stepwise model and adjusted were age, BMI, time since menopause, physical exercise, ethnicity, marital status, oc-cupation, smoking, use of medication, hormone therapy, osteoporosis, muscle strength, flexibility, and balance. Binary logistic regression showed that the vari-ables associated with falls were muscle strength of the lumbar spine and the presence of osteoporosis. Greater lum-bar spine strength was associated with a decreased risk for falls (OR, 0.97; 95% CI: 0.95, 0.99), while the presence of os-

taBLe 2Muscle Strength and Flexibility in

Postmenopausal Women With (n = 133) and Without Osteoporosis (n = 133)

* Data presented as mean SD.† Generalized linear model procedure to control for variables: age, body mass index, school education, time since amenorrhea, and physical exercise.

With osteoporosis* Without osteoporosis* P value†

Muscle strength

Lumbar spine (kg) 33.4 11.8 40.0 14.5 .06

Lower limbs (kg) 33.6 11.8 40.8 14.7 .02

Flexibility

Trunk flexion (°) 81.2 16.7 82.6 16.0 .62

Trunk extension (°) 20.3 8.3 18.7 7.3 .01

taBLe 1Characteristics of Postmenopausal Women With

(n = 133) and Without Osteoporosis (n = 133)

* Data presented as mean SD.† Mann-Whitney test.

With osteoporosis* Without osteoporosis* P value†

Age (y) 66.0 4.5 64.9 4.4 .03

Age at menopause (y) 46.4 6.2 49.2 4.8 .01

Body mass index (kg/m2) 27.5 4.8 29.8 5.1 .01

Bone mass density (g/cm2) 0.8 0.1 1.2 0.1

T-score (young adult) –2.9 0.4 0.0 0.9


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[ research report ]without osteoporosis. Few studies have assessed the intrinsic risk factors for falls specifically in women with osteoporosis. Sinaki et al26 studied women with osteoporosis and found that they had a greater propensity for falling, lower grip strength, lower trunk extension muscle strength, and lower-limb muscle strength compared to women without osteoporosis. These data on muscle strength of the lower limbs are consistent with the results of the present study.

Regarding muscle strength, studies conducted in postmenopausal women28 and in the elderly in general22 indicate that lower-limb strength that falls below a certain threshold may predispose an individual to falls. In contrast, Keskin et al14 analyzed muscle strength of the lower limbs in older women and observed no difference in this variable among indi-viduals with a history of falls. Although lower-limb muscle strength has been implicated as a risk factor for falls in the elderly, some studies have found no asso-ciation between falls and this variable,14,17 similar to the results of this study.

Differences on the impact of lower-muscle strength on falls found in previous studies may be the result of the popula-tions studied. For example, Sinaki et al26 included only women with osteoporosis who had spinal kyphosis. It is well known that spinal deformities, such as kyphosis, are associated with structural changes of the spinal column, vertebral compression fractures, and decreased strength of the trunk extensor muscles.26 The present study did not include women with exces-sive kyphosis, which may explain the little difference in the strength of the lumbar spine between the groups. Neverthe-less, the correlation analysis showed falls to be negatively correlated with muscle strength of the lumbar spine.

Correlation analysis also showed that falls correlated with trunk flexion range of motion. It is known that muscles and tendons tend to become more rigid with aging, resulting in decreased flexibil-ity.13 Intervertebral disc degeneration is also a factor limiting range of motion.31

teoporosis increased fall risk by a factor of 2.17 (95% CI: 1.29, 3.65) (taBLe 4).

discUssion

the aim of this study was to de-termine the association between the occurrence of falls and a group

of specific intrinsic risk factors for falls in postmenopausal women with and without osteoporosis. Significantly more women (51%) in the group with osteo-porosis had a history of 1 or more falls

within the previous year compared to the group without osteoporosis (29%). These data were similar to those of other stud-ies showing that the history of 1 or more falls occurring in 1 year in all elderly is approximately 38% compared with 30% in women with osteoporosis.1,2

Fall risk depends on both intrinsic and extrinsic factors. In the present study, the intrinsic factors evaluated showed decreased lower-limb strength and greater flexibility of trunk extension in women with osteoporosis than in women

taBLe 4Binary Logistic Regression Analysis for

Variables Associated With Falls in Postmenopausal Women (n = 266)*

Abbreviation: CI, confidence interval; OR, odds ratio.* Binary logistic regression with stepwise variable selection criteria. Dependent variable: fall (binary). Independent variables: age, body mass index, time since menopause, physical exercise, ethnicity, mari-tal status, occupation, smoking, use of medication, hormone therapy, osteoporosis, muscle strength, flexibility, and balance.

variables P value or (95% ci)

Muscle strength for lumbar spine extension .01 0.97 (0.95, 0.99)

Osteoporosis .01 2.17 (1.29, 3.65)

taBLe 3Correlation Between Muscle Strength, Flexibility, and Balance With Falls in

Postmenopausal Women*

* Adjusted by group with (n = 133) and without (n = 133) osteoporosis.† Spearman's correlation coefficient adjusted for age, body mass index, school education, time since menopause, physical exercise, and osteoporosis.

variables r† P value

Muscle strength

Lumbar spine (kg) –0.13 .03

Lower limbs (kg) –0.10 .11

Flexibility

Trunk flexion (°) –0.13 .04

Trunk extension (°) –0.09 .15

Balance

Amplitude of movement lateral, eyes open (cm) –0.00 .97

Amplitude of movement lateral, eyes closed (cm) –0.03 .61

Amplitude of movement anterior-posterior, eyes open (cm) –0.05 .44

Amplitude of movement anterior-posterior, eyes closed (cm) 0.02 .73

Ellipse area (cm2), eyes open 0.03 .62

Ellipse area (cm2), eyes closed 0.05 .43

Velocity (cm/s), eyes open 0.09 .16

Velocity (cm/s), eyes closed 0.04 .47

correlation With Falls


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guide intervention strategies to prevent falls and their consequences. t

KeY PointsFindinGs: A greater percentage of women with postmenopausal osteoporosis had a history of 1 or more falls within the previous year compared to women without osteoporosis. Among those who fell, the incidence of recurrent falls was also greater for the women with osteo-porosis. Muscle weakness of the lumbar spine and the presence of osteoporosis are intrinsic factors associated with the risk of falls.iMPLication: These results may serve to guide intervention strategies to prevent falls and their consequences in women with osteoporosis who are at greater risks of fall-related fractures.caUtion: Long-term studies with more subjects are needed to determine if these results could be applied to a larger population.

eyes open. However, there was no asso-ciation between measures of balance and the occurrence of falls, and there were no studies in the literature that evaluated stabilometric data in individuals with osteoporosis for comparison purposes. Melzer et al17 tested elderly individuals (mean age, 78 years) on a force platform using a wide base of support. The authors found no association between the stabi-lometric parameters and the occurrence of falls. Findings of the current study are in agreement with those of other authors who also failed to observe differences in balance parameters and the occurrence of falls.14,17

The diversity of study results may be explained by other variables such as dif-ferences in mean age, dwelling location (in a community or nursing home), life-style of the participants, and the tech-niques employed to assess the variables analyzed. This suggests that there may be many interactive causal factors for falls that need further investigation, and it emphasizes the complex interaction be-tween intrinsic and extrinsic factors as-sociated with falls.

The main limitation of this study was the assessment of falls based upon self-report. This might have influenced the estimation of fall occurrence data. More-over, it is important to note that the study was performed with community-dwelling women, using objective tests to evaluate all the variables studied.

concLUsions

a greater percentage of women with postmenopausal osteoporo-sis had a history of 1 or more falls

within the previous year and a higher risk of recurrent falls than women without os-teoporosis. Moreover, muscle strength of the lumbar spine and the presence of os-teoporosis are intrinsic factors associated with the risk of falls. The results of this study may guide future studies investi-gating a cause-and-effect relationship among factors related to falls in indi-viduals with osteoporosis. This will help

Furthermore, the literature shows that weakness of trunk extensor muscles in individuals with osteoporosis leads to a decrease in trunk extension range of motion.7

In the present study, the differences between absolute values for flexibility angles were very small and had no clini-cal significance. We believe that the small numerical difference (1.6°) in trunk ex-tension angles between the groups (mean SD, 20.3 8.3 versus 18.7 7.3) is within the range of error for that measure.

Advancing age and the presence of certain degenerative diseases of the lo-comotor system, such as osteoporosis, may decrease flexibility and indepen-dence of movements. The greatest re-sulting concerns are related to gait, and the contribution to a higher risk of falls and fractures.30 The logistic regression analysis showed that increasing strength of the lumbar spine by 1 unit would de-crease the risk of falls (OR, 0.97), while the presence of osteoporosis increases the risk (OR, 2.17). Although multiple factors contribute to falls, a decrease in balance has been cited as an important element.17 Lynn et al16 observed differenc-es in strategies for balance control among individuals with and without osteoporo-sis. In particular, those with osteoporosis are better at using strategies involving the hip to maintain balance compared to normal individuals.

The erect posture is not a static event and is characterized by sway, which maintains the body in continuous move-ment. Postural sway is involuntary and depends on action of the sensory system (visual, vestibular, and proprioceptive), processing in the central nervous system, and neuromuscular system.11 Sway may be quantified on a force platform used to record center-of-pressure movements on surface planes in both the anterior-poste-rior and lateral directions. In the present study, the only difference observed in bal-ance measurements between groups was in the amplitude of sway in the anterior-posterior direction when measured with

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Predictors of falls in women

Health & Medicine

Transcript of Predictors of falls in women