Postural changes versus balance control and falls in community-living older adults : a systematic review Alterações posturais versus controle do equilíbrio e quedas em idosos da comunidade : Revisão sistemática

Abstract Introduction: Since falls are considered to be a public health problem, it is important to identify whether postural changes over time contribute to the risk of falls in older adults. Objective: To investigate whether postural changes increase fall risk and/or postural imbalance in healthy, community-dwelling older adults. Methods: In April 2016, two reviewers independently searched the PubMed, Web of Science, SPORTDiscus, and CINAHL databases for studies in English published in the previous 10 years, using the following combined keywords: “posture” or (“kyphosis”,“lumbar lordosis”,“flexed posture”,“spinal curvature”,“spinal sagittal contour”) AND “elderly” AND “fall”. Study quality was assessed according to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for observational studies. Results: The search retrieved 1,734 articles. Only observational studies that assessed posture, balance, and/or falls in older adults were considered eligible for review. The final sample included 17 articles: reliability and reproducibility of the instruments were not reported in five studies, while two studies offered a questionable description of the instruments used. Fourteen


Introduction
Falls are considered to be an important public health problem due to the risks of morbidity and mortality [1].In Brazil, about 30% of community-living older adults report falling at least once a year [2 -4].
In addition to environmental risks [5], the literature points out several risk factors intrinsic to falls, such as age, female gender, functional disability, balance deficit, gait disorders, sedentary lifestyle, poor health self-perception, use of psychotropic drugs, muscle weakness, reduced visual acuity, cognitive deficits, and polypharmacy [1 -7].
Although posture is not considered a risk factor for falls, several studies investigated the relationship between posture and body balance and/or falls in older adults [8 -12].The Guide to Physical Therapist Practice of the American Physical Therapy Association (APTA) defines posture as "the alignment and positioning of the body in relation to gravity, center of mass, or base of support" [13].In ideal posture, there is a state of muscular and skeletal equilibrium and an adequate tension on support structures for a more efficient balance control [13].
Ideal postural alignment is indirectly associated with aging [8,12,14].The body undergoes changes in the bones, muscles, and joints that lead to changes in the physiological spinal curvature [10,13].Thoracic hyperkyphosis is the most common, affecting 20 -40% of older adults worldwide [15], along with osteoporosis as an associated clinical condition [16].Patients with hyperkyphosis may have anterior displacement of the head, protrusion Fisioter Mov.2018;31:e003125 of the scapula, loss of lumbar lordosis [17], and, consequently, anteriorly project into the line of the center of gravity [8].Changes in the projection of the center of gravity negatively affect body balance control [17].
The relationship between body balance and postural changes in the vertebral column due to the clinical condition of osteoporosis was also highlighted in the reviews by Hsu et al. [17] and Groot et al. [18].These authors found poor balance control in patients with vertebral fractures, thoracic hyperkyphosis, and flexed posture.
A gap exists in the literature for systematic reviews to investigate how changes in postural alignment of different body segments affect postural stability and the risk of falls in healthy older adults.Thus, this study aimed to investigate whether postural changes increase fall risk and/or postural imbalance in healthy, community-dwelling older adults.

Search Strategy
In April 2016, two reviewers independently searched PubMed, Web of Science, SPORTDiscus, and CINAHL for studies in the last 10 years.After screening titles, abstracts and keywords, fulltext versions of potential papers were selected.Discrepancies were resolved by a third reviewer.The following keywords (DESCs and MESH terms) and search strings were used: (posture OR kyphosis OR lumbar lordosis OR flexed posture OR spinal curvature OR spinal sagittal contour AND elderly AND fall).

Selection/Inclusion Criteria
The inclusion criteria were English written observational studies assessing posture, balance, and/or falls in adults 60 years and older.We excluded duplicates, reviews, case studies, theses and dissertations, studies with special populations such as those with a specific pathology (for instance, Parkinson's disease, stroke, osteoporosis, etc.), and articles not available in full text.

Quality assessment
Study quality was assessed according to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for observational studies (Table 1) [19].(To be continued)

Characteristics of the studies retrieved
Figure 1 shows a flowchart describing the results of each step in the selection procedure.Of 1,734 articles retrieved, 17 were eligible for inclusion.Fifty per cent of the studies included in this review were conducted in Japan, while the remaining studies were representative of different geographical locations (Australia, USA, Netherlands, Italy, Japan, Malaysia, Poland).
The articles were analyzed with regard to design, sample characteristics, tools used to assess body posture, balance and/or falls risk, and outcomes (Table 2).Three studies have specifically assessed the feet and the ankles and their data are shown separately in Table 3.
Falls were ascertained by the administration of a questionnaire, and assessed using the Falls Efficacy Scale (FES) [30].Participants' falls risk was assessed using Pluijm's assessment [26] and the Physiological Profile Assessment (PPA) [34].While most studies followed participants for 12 months [10,21,24,28,34], in one study participants were followed for only six months [27].

Discussion
Thus, this systematic review aimed to investigate whether postural changes increase fall risk and/or postural imbalance in healthy, community-dwelling older adults.In total, 17 articles were eligible and included for review.They used different tools to assess body posture, not only at the vertebral level, but also at the level of the ankles and the feet.
Postural deformities, such as thoracic hyperkyphosis, flexed posture, loss of lumbar lordosis, forward trunk inclination, and decreased plantar arch negatively affected postural balance and risk of falls in healthy older adults.Our findings are in line with those reported by Groot, Van der Jagt-Willems [18], in which postural control was affected in osteoporotic older adults with vertebral fractures, thoracic hyperkyphosis and flexed posture.
Most of the studies measured thoracic kyphosis [21 -24, 26 -31].Thirty-six percent of older adults with thoracic hyperkyphosis had experienced falls and were 1.32 times more likely to report a fall in the past year than were those with normal kyphosis [28].According to Kado [15], the relationship between thoracic hyperkyphosis and falls in women could be explained by age.In the study by Van der Jagt-Willems et al. [27], patients with hyperkyphosis were twice more likely to fall than their counterparts, regardless of sex.In contrast, Kasukawa et al. [21] and Ishikawa, Miyakoshi et al. [22] found no correlation between falls and increased thoracic hyperkyphosis.
Thoracic hyperkyphosis, flexed posture and forward trunk inclination are changes in the sagittal plane of the vertebral column that lead to a forward projection of the gravity line, negatively affecting postural balance [37,38].This is confirmed by the findings of this review, in which poorer stabilometry results were associated with postural malalignment and falls [21,22,24,29,31].Previous studies have also associated thoracic hyperkyphosis with loss of mobility, reduced quality of life and increased falls risk in osteoporotic older adults [11,16,39,40].
A relevant finding of this systematic review is that balance and risk of falls in older adults is not only affected by thoracic deformities such as thoracic hyperkyphosis.Special attention should be given to the lumbar spine, because several studies found an association between changes in lumbar curvature and poorer balance-test performance (as measured by stabilometry) and increased incidence of falls in healthy older adults [21 -24, 31, 32].
Loss of lumbar lordosis leads to pelvic retroversion and posterior shift of the gravity line [38].In the study by Ishikawa et al. [10], loss of lumbar lordosis increased postural instability and propensity to fall in older adults with osteoporosis.Thus, both thoracic hyperkyphosis and loss of lumbar lordosis induce a displacement of the gravity line (GL) in the sagittal plane, reducing stability limits in all directions, as well as the magnitude of response and displacement speed, especially in the antero-posterior axis, fostering an increased postural balance in older adults [37].
Thus, the ankles and feet should also be taken into account when analyzing the influence of posture on balance and the risk of falls in healthy older adults.The feet play an important role in body stabilization, since it contributes to weight load distribution in the bipedal position and influences balance and balance control during gait [34,41].Studies have associated foot characteristics with the risk of falls in older adults.Loss of ankle mobility and plantar tactile sensation, deformities and toe weakness were found to negatively affect balance, gait speed and functional mobility test performance [7,41,42].
The maintenance of body balance depends on a complex, coordinate interaction of vestibular, somatosensory and visual systems, which hold the body's center of mass over the base of support [43].This is why the use of multidimensional measures has been advocated for the assessment of balance and risk of falls in older adults.The Clinical Guidance Statement on Management of Falls [44] recommends the screening of different risk factors for falls and interventions, such as foot assessment and footwear correction, with level two evidence.It is important to highlight that other variables associated with postural changes may influence balance impairment and risk of falls in older adults, such as visual and proprioceptive muscle response [31], paravertebral muscle weakness [21 -24], decreased spinal mobility [21] and low physical function [8].
Although postural alignment changes with ageing, stretching and strengthening exercise programs to paravertebral muscles may help to prevent or minimize these changes.In a twelve-month follow-up study, Pawlowsky et al. [45] found that older women receiving in-home physical therapy sessions twice a week for 12 months showed improved paravertebral strength and flexibility, and reduced thoracic kyphosis by 3°.Similar results were found in the study by Katzman et al. [46] with hyperkyphotic older women.
Despite the complexity of postural control and balance maintenance mechanisms in healthy older adults, this review shows that postural assessment in older adults should be part of the daily clinical routine of physical therapists, as a variable that still needs to be investigated as a risk factor for falls in healthy older adults.Moreover, exercise programs that contribute to increasing paravertebral muscle strength and flexibility should be included in the therapy prescribed by physical therapy professionals.Some of the limitations of the studies included in this review were, first, the great variability of methods used to assess posture -ranging from more subjective (visual postural assessment) to more accurate technologies (SpinalMouse); second, the great variability of tools used to assess balance -from stabilometry to functional tests; third, some authors did not describe the reliability and reproducibility of the assessment tools; and, finally, the fact that some studies were cross-sectional and therefore did not assess the cause-effect relationship between postural changes, and/or impaired balance in communityliving older adults.

Conclusion
This review shows that there is evidence that postural changes such as thoracic hyperkyphosis, loss of lumbar lordosis and decreased plantar arch seem to contribute to the increased postural instability and consequently an increased risk of falls in communityliving older adults.However, since there is no Fisioter Mov.2018;31:e003125 consensus on the best method to assess balance in older adults, further studies should be conducted to elucidate this issue.Moreover, longitudinal studies need to be conducted to investigate the causeeffect relationship between age-related postural changes, and balance and falls in community-living older adults.

Figure 1 -
Figure1-Flowchart of the selection process using the PRISMA criteria[20].

Table 1 -
The STROBE checklist for assessment of methodological quality of observational studies

Table 1 -
The STROBE checklist for assessment of methodological quality of observational studies

Table 1 -
The STROBE checklist for assessment of methodological quality of observational studies

Table 2 -
Characteristics of the studies with regard to methodologies, sample profile, outcomes and tools used for assessing body posture, balance and falls risk Fisioter Mov.2018;31:e003125

Table 2 -
Characteristics of the studies with regard to methodologies, sample profile, outcomes and tools used for assessing body posture, balance and falls risk

Table 2 -
Characteristics of the studies with regard to methodologies, sample profile, outcomes and tools used for assessing body posture, balance and falls risk Fisioter Mov.2018;31:e003125

Table 2 -
Characteristics of the studies with regard to methodologies, sample profile, outcomes and tools used for assessing body posture, balance and falls risk

Table 3 -
Characteristics of the studies with regard to methodologies, sample profile, outcomes and tools used for assessing the feet and the ankle, as well as balance and falls risk Fisioter Mov.2018;31:e003125