emphasis on the neurologic and musculoskeletal changes that effect fall risk. These changes will be discussed by the system primarily involved in maintaining upright posture. Other bodily systems, such as the cardiopulmonary and endocrine systems, also experience age-related changes, but do not Neurologic changes Changes in postural control that can lead to falls in an older adult population, in both the central and peripheral nervous systems, can be either attributed to typical decline due to aging and/or the presence of disease. As mentioned earlier, the presence of chronic disease can increase fall risk, but when coupled with typical neurologic changes due to aging, this risk multiplies. Changes in postural control Although the overall population of older adults is a very heterogeneous group with a wide variety of aging consequences, there are specific changes in older adults that impact postural control (Shumway-Cook & Woollacott, 2017). Some of these include: ● Delay in ankle, hip, stepping strategies. ● Balance strategies activated out of sequence, or in an inefficient or ineffective manor. ● Increased sway in quiet stance with impairments in at least two sensory systems, and especially when relying on vestibular inputs only. ● Slower adaptation to new environments (lighting, surface, visual stimulation). ● Decreased anticipatory postural abilities during functional tasks. ● Difficulty dual-tasking during mobility. With aging, motor control becomes more reliant on central mechanisms, especially prefrontal and basal ganglia (Seidler et al., 2010), making dual-tasking increasingly difficult. Older adults engage these central nervous system (CNS) structures to compensate for age-related sensorimotor declines, but as we age, cortical shrinking occurs, synaptic connections become more inefficient, and neurotransmitter amount and usage declines. This all spells trouble for an older adult who is attempting to carry a heavy load from an unfamiliar store to their car in the dark, while talking to a friend. Performing multiple tasks in new or challenging situations is a recipe for falls in many older adults, especially those with presence of disease or comorbidities that affect postural control. The paradox of this aging dilemma is that the prefrontal structures required to maintain balance and cognitive control show the largest age- related differences. Older adults are relying on diminishing CNS cognitive resources, thus are at increased risk for falls. Specific screening techniques for changes in postural control will be addressed in a later section and will include tests such as the modified Clinical Test for Sensory Interaction in Balance, the Timed Up and Go (TUG) Cognitive test, and the BestTEST. Sensory changes Although all senses are affected by aging to some degree, those that most directly affect fall risk include vision, somatosensation, and vestibular function. These senses should provide the CNS with an accurate picture of where the body is in space and whether it is stationary or in motion (Shumway-Cook & Woollacott, 2007). When all three senses are working normally, adults should have adequate postural control for a variety of tasks and environments through the ability of the CNS to modify reliance on a particular system, also called sensory reweighting (Oie, Kiemel, & Jeka, 2002). This sensory weighting hypothesis suggests that the CNS integrates all sensory input and then decreases the “weight” or attention given in inaccurate sensory inputs during a postural control task, while increasing weight or attention given to more accurate senses. Age-related changes in vision, somatosensation, and/or vestibular input can influence sensory integration demands on the CNS and should be considered during a fall risk assessment for older adults. Other senses such as hearing, taste, and smell have a lesser impact
have as significant an effect on fall risk as the neurologic and musculoskeletal systems, thus the emphasis on the latter two systems. Screening and assessment of these systems will be covered in later sections.
on fall risk, but are discussed here as they may indirectly affect safety and nutrition. Vision Aging is associated with loss of visual acuity, development of cataracts, macular degeneration, glaucoma, and other less common visual conditions that increase risk for falls. Overall visual acuity diminishes; presbyopia or “near vision” is decreased; pupil diameter decreases, reducing light to the retina by one-third that of younger adults; lens yellowing increases, which decreases light and increases glare; contrast sensitivity declines, making it difficult to see in dimly lit settings; impairments in depth perception occur; and a general loss in the visual field occurs. The overall result for older adults is an increased need for more light to see clearly and function safely. Adults who report problems or have abnormal visual screening results should be referred for a formal vision assessment. It is unclear whether visual correction alone will decrease risk for falls, but the literature is clear that vision assessment and correction should be part of a multifactorial fall risk intervention (AGS/BGS, 2010). Somatosensory system Older adults experience somatosensory changes that can be attributed to typical aging or to conditions such as diabetes mellitus or spinal stenosis. Older adults can experience up to a 30% decline in cutaneous sensitivity due to normal aging, along with a decline in vibratory sensitivity that can change as much as three times the normal amount by 90 years of age (Shumway-Cook & Woollacott, 2007). Additionally, pain and temperature sensitivity can become less acute and proprioception and position sense can decline with age. Declines in nerve conduction velocity also may result from aging in the peripheral nervous system (PNS) and the CNS. The basic result for older adults is some degree of peripheral neuropathy in various sensory modalities, depending on the presence of comorbidities in union with the aging process. Although existing clinical guidelines do not address assessment of somatosensation, clinicians should screen for the presence of sensory loss, especially in the soles of the feet. These sensory changes in the foot may lead to unsafe choices in footwear, which can contribute to fall risk (AGS/BGS, 2010). Most studies recommend a foot assessment that identifies the presence of serious foot problems such as severe bunions, toe deformities, ulcers or deformed nails, or changes in position sense. This also should include an assessment of the quality and appropriateness of footwear. Vestibular system The vestibular system’s job is to estimate body and head position and motion (Herdman & Clendaniel, 2014). It provides structures in the CNS, such as the cerebellum and vestibular nuclear complex, with inputs from the inner ear, proprioception from the areas such as the cervical spine, visual signals, and motor intentions to help generate accurate motor commands. This system is normally very accurate. Unfortunately, declines in the effectiveness and accuracy of the vestibular system affect almost all older adults. By 70 years of age, the typical adult experiences a 40% loss of vestibular hair and nerve cells. These PNS structures help to detect changes in head motion, which are crucial for normal postural control. These changes also are accompanied by 3% loss per decade of vestibular nucleus cells in the CNS that occur from 40 to 90 years of age. As older adults experience reduced ability to resolve conflicting sensory inputs from the visual, vestibular, and somatosensory systems, maintaining postural control becomes more difficult and can result in falls. Overall, there is an increased incidence
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