2. Postural balance

fall at least once and 10–20% fall twice or more [3]. The incidence among institutionalized older people is even higher, with a mean percentage of residents who fall

each year of over 40% [4].

Geriatric Medicine and Gerontology

Figure 1.

Figure 2.

176

Total population by broad age group. Courtesy: World Health Organization.

Life expectancy at birth by sex. Courtesy: World Health Organization.

Balancing is the process of controlling the body's center of mass with respect to its base of support, whether in a static or dynamic situation. It depends on the integration of sensory systems with the CNS. Sensory information from somatosensory, visual, and vestibular systems must be integrated to interpret complex sensory environments. Each system interacts with each other to maintain balance in a closed loop, with an interrelation of cause and effect. When the sensory environment is changed, the CNS needs to re-weigh the contribution of each of the senses in postural balance. In an environment with good lighting and a firm surface, the contribution of somatosensory information is 70%, the visual information is 10%, and the vestibular information is 20% [5].

Each system is prone to deterioration with advancing age, and this is influenced by age-related diseases and use of some types of medications, in addition to polypharmacy [6]. Systems can partially compensate for each other's deterioration. Failing compensation strategies may eventually result in impaired balance, which may result in falls [7].

#### 2.1 Vision and postural balance

The role of central and peripheral vision information in the control of movements and posture was examined in some studies [8, 9]. These authors suggested that peripheral vision is used for postural control and most particularly for stabilization of fore-aft sways, while the central vision is more often used for foot trajectory planning, targeting, obstacle avoidance, and stabilization of lateral sways.

Visual impairment is an important health problem and a major cause of injury in the elderly. Cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy are the most common diseases related to the elderly and can interfere with the postural balance.

#### 2.1.1 Cataract

Cataract, affecting mainly visual acuity and contrast sensitivity, contributes to about 50% of visual impairments in the elderly [10, 11]. The consequences include decreased ability to perform activities of daily living (such as reading, watching television, driving, and interacting socially), depression, increased number of falls, and increased mortality [10, 12]. The impact on patients is comparable with that of major systemic conditions including stroke, diabetes, and arthritis. In a study in patients with cataract, Pasma et al. found a higher proprioceptive weight compared with healthy elderly participants, which means that the elderly with cataract rely more on their proprioceptive information [7].

#### 2.1.2 Glaucoma

Glaucoma is a progressive optic neuropathy characterized by degeneration of retinal ganglion cells and their axons with consequent vision loss and blindness. This condition leads to a characteristic reduction in the visual field (VF), with good central visual acuity. Previous studies have reported a higher risk of falling in patients with glaucoma compared to normal subjects [13–15]. In the study by Black et al., a cohort of glaucoma subjects was examined to assess body displacement of the trunk and the results showed that the worse the visual field defect, the greater the body sway [16].

#### 2.1.3 Age-related macular degeneration

Age-related macular degeneration (AMD) is a disease that affects the macula (central vision), altering the accuracy of vision necessary for "direct" and fine activities, and may interfere with activities of daily living [17].

Wood et al. studied postural balance in older adults with AMD and showed that diminution of contrast sensitivity and visual field loss lead to postural instability and mobility difficulties in these patients [18]. Chatard et al., studying 10 elderly unilateral AMD subjects, 10 elderly bilateral AMD subjects, and 10 healthy age-matched control subjects, showed that bilateral AMD subjects had a surface area and an antero-posterior displacement of the CoP higher than healthy elderly. Unilateral AMD subjects had more antero-posterior displacement of the CoP than healthy elderly [19]. The authors conclude that because of aging, AMD subjects could have poor postural adaptive mechanisms which increase instability and risk of falls.

#### 2.1.4 Diabetic retinopathy

Diabetic retinopathy (DR) is a common and potentially blinding microvascular complication of diabetes [20]. In a study, Gupta et al. found that diabetes per se was not a risk factor for falls. However, the authors found an association between diabetic patients with DR and risk of falling [20], suggesting a relation between DR and postural balance.

The greater tendency to fall in patients with mild-to-moderate DR can be explained by a reduction in the components of the visual function system, such as contrast, sensitivity, stereo acuity, and color perception [21, 22].

Figure 3 summarizes the normal vision and main eye disorders that can interfere with the postural balance described above.

Thus, it is important to evaluate visual function when we propose to work with postural balance in the elderly.

#### 2.2 Vestibular system and postural balance

Through its sensory functions, the vestibular system detects the position and movement of the head in space relative to gravity, and helps to stabilize vision and balance [23].

The vestibular system has structures similar to miniaturized accelerometers, which report continuous information to the cerebral cortex, cerebellum, and somatic sensory cortices on the movements and position of the head and body. The vestibular nuclei make connections with structures of the brainstem and cerebellum and also innervate the motor neurons that control extraocular, cervical, and postural muscles [23] (Figure 4).

The proprioceptive information depends on muscle spindles, the Golgi tendon organ (GTO), and articular receptors. The first provide the nervous system with information about the muscle's length and velocity of contraction, thus contributing to the individual's ability to discern joint movement and position sense [28]. Besides, the muscle spindles provide afferent feedback that translates stimuli to appropriate reflexive and voluntary movements. The GTO relays information about tensile forces, and is sensitive to very slight changes [28], and when it is activated, the afferent neuron synapses in the spinal cord interneurons, which inhibit the muscle alpha motoneuron, resulting in decreased tension in muscle and tendon. Articular or joint proprioceptors respond to mechanical deformation of the joint

The main vision impairments that interfere with balance. Courtesy: National Eye Institute, National Institutes

On a slippery or dry floor surface, people show different gait parameters, including step length, required coefficient of friction, and heel contact velocity, evidencing the importance of the sensorimotor system in balance control [29].

Sensorimotor impairments occur with aging and are believed to contribute to the increased likelihood of imbalance and falling [30]. Damage to joint and muscular

capsule and ligaments.

Figure 3.

179

of Health (NEI/NIH).

Postural Imbalance in the Elderly: Main Aspects DOI: http://dx.doi.org/10.5772/intechopen.79830

Impaired function of the vestibular system causes vertigo, loss of balance, and loss of gaze fixation during movement, often accompanied by dizziness and nausea [24].

Vestibular dysfunction is typically characterized by vertigo (i.e., an illusory sense of motion) and imbalance owing to disturbances in gaze and postural stability [25], which can culminate in falls [26].

So, the evaluation of the vestibular system is indispensable when the patients have a impaired balance control.

#### 2.3 Somatosensory system and postural balance

People rely primarily on the proprioceptive and cutaneous input to maintain normal quiet stance and to safely accomplish the majority of activities of daily living [27]. Postural Imbalance in the Elderly: Main Aspects DOI: http://dx.doi.org/10.5772/intechopen.79830

#### Figure 3.

2.1.3 Age-related macular degeneration

Geriatric Medicine and Gerontology

2.1.4 Diabetic retinopathy

DR and postural balance.

postural balance in the elderly.

tural muscles [23] (Figure 4).

[25], which can culminate in falls [26].

2.3 Somatosensory system and postural balance

have a impaired balance control.

balance [23].

178

with the postural balance described above.

2.2 Vestibular system and postural balance

Age-related macular degeneration (AMD) is a disease that affects the macula (central vision), altering the accuracy of vision necessary for "direct" and fine

Wood et al. studied postural balance in older adults with AMD and showed that diminution of contrast sensitivity and visual field loss lead to postural instability and mobility difficulties in these patients [18]. Chatard et al., studying 10 elderly unilateral AMD subjects, 10 elderly bilateral AMD subjects, and 10 healthy age-matched control subjects, showed that bilateral AMD subjects had a surface area and an antero-posterior displacement of the CoP higher than healthy elderly. Unilateral AMD subjects had more antero-posterior displacement of the CoP than healthy elderly [19]. The authors conclude that because of aging, AMD subjects could have poor postural adaptive mechanisms which increase instability and risk of falls.

Diabetic retinopathy (DR) is a common and potentially blinding microvascular complication of diabetes [20]. In a study, Gupta et al. found that diabetes per se was not a risk factor for falls. However, the authors found an association between diabetic patients with DR and risk of falling [20], suggesting a relation between

Figure 3 summarizes the normal vision and main eye disorders that can interfere

Thus, it is important to evaluate visual function when we propose to work with

Through its sensory functions, the vestibular system detects the position and movement of the head in space relative to gravity, and helps to stabilize vision and

The vestibular system has structures similar to miniaturized accelerometers, which report continuous information to the cerebral cortex, cerebellum, and somatic sensory cortices on the movements and position of the head and body. The vestibular nuclei make connections with structures of the brainstem and cerebellum and also innervate the motor neurons that control extraocular, cervical, and pos-

Impaired function of the vestibular system causes vertigo, loss of balance, and loss of gaze fixation during movement, often accompanied by dizziness and nausea [24]. Vestibular dysfunction is typically characterized by vertigo (i.e., an illusory sense of motion) and imbalance owing to disturbances in gaze and postural stability

So, the evaluation of the vestibular system is indispensable when the patients

People rely primarily on the proprioceptive and cutaneous input to maintain normal quiet stance and to safely accomplish the majority of activities of daily living [27].

The greater tendency to fall in patients with mild-to-moderate DR can be explained by a reduction in the components of the visual function system, such as

contrast, sensitivity, stereo acuity, and color perception [21, 22].

activities, and may interfere with activities of daily living [17].

The main vision impairments that interfere with balance. Courtesy: National Eye Institute, National Institutes of Health (NEI/NIH).

The proprioceptive information depends on muscle spindles, the Golgi tendon organ (GTO), and articular receptors. The first provide the nervous system with information about the muscle's length and velocity of contraction, thus contributing to the individual's ability to discern joint movement and position sense [28]. Besides, the muscle spindles provide afferent feedback that translates stimuli to appropriate reflexive and voluntary movements. The GTO relays information about tensile forces, and is sensitive to very slight changes [28], and when it is activated, the afferent neuron synapses in the spinal cord interneurons, which inhibit the muscle alpha motoneuron, resulting in decreased tension in muscle and tendon. Articular or joint proprioceptors respond to mechanical deformation of the joint capsule and ligaments.

On a slippery or dry floor surface, people show different gait parameters, including step length, required coefficient of friction, and heel contact velocity, evidencing the importance of the sensorimotor system in balance control [29].

Sensorimotor impairments occur with aging and are believed to contribute to the increased likelihood of imbalance and falling [30]. Damage to joint and muscular

essential to evaluate the visual system, the vestibular and auditory system, and the

A comprehensive assessment of balance is important for both diagnostic and

The tests can be divided between single-task measures and multiple-task measures [36]. These tests often can be done very quickly and with relatively little

The single leg-stance test (SLS) is simple, has high reliability and low cost, and

is widely used for diagnosis and follow-up of patients in research and clinical settings. In this test, the participant remains supported on one leg, with arms resting on the hips, and the time (in seconds) that the patient remains in the position without unbalance is verified [37]. Decreased eyes-open SLS time is associated

The functional reach test (FRT) is an easy and inexpensive test in which the patient flexes the trunk, extending the arms horizontally and keeping the feet in contact with the ground. The score is obtained by measuring the distance between the initial and the final positions of the fingertip [39]. Displacements less than 15 cm

The gait speed test gives an easy, inexpensive, reliable measure of functional capacity [41], with high interrater and test-retest reliability [42]; does not require laboratory equipment; is not limited to a specific health care discipline [43]; and may be done quickly in clinical settings. The test may vary according to the pace (usual or maximal speed), whether static or moving start, and the distance walked (ranging

The Berg Balance Scale (BBS) consists of a battery of 14 tasks common to the activities of daily living, which quantitatively evaluate the risk of falls, through observations undertaken by the examiner [45]. The score on the test ranges from 0 to 56 and the performance on each task is measured on a five-point scale ranging from 0 to 4 (0 = unable to perform, 4 = independent). Scores of 48 or less indicate

indicate postural balance problems and increased risk of falls [40].

sensorimotor system.

equipment and training.

3.2.1 Single-task measures

3.2.1.1 Single-leg stance test

3.2.1.2 Functional reach test

3.2.1.3 Gait speed test

from 4 to 500 m) [44].

3.2.2 Multiple-task measures

3.2.2.1 Berg Balance Scale

181

with an increased risk for falls [38].

3.2 Functional performance tests

therapeutic reasons in clinical practice.

Postural Imbalance in the Elderly: Main Aspects DOI: http://dx.doi.org/10.5772/intechopen.79830

Figure 4.

Postural balance and the vestibular system responses. From Wikimedia Commons, https://commons.wikimedia. org/wiki/File:1410\_Equilibrium\_and\_Semicircular\_Canals.jpg.

proprioception, strength (capacity of muscle strength), and reaction time may contribute to the increase in the probability of fall [30].

Some diseases can affect muscles and joints. Studies have shown that, in patients with knee osteoarthritis (AO), postural balance is impaired due to reduced quadriceps function and decreased proprioception [31, 32]. Among elderly individuals, the prevalence of knee OA is approximately 12.2%, with a higher prevalence in women (14.9%) than in men (8.7%) [33].

Patients with neuromuscular diseases (NMDs), usually characterized by muscle weakness, appear to fall regularly. Aging causes a loss of muscle mass with a preferential decline in type II fibers [34], besides decrements in force production, power, specific tension, and fatigability [35], increasing the risk of falls.

#### Key points

