CNS auditory neural cell deterioration. These sensory changes make it difficult for older adults to hear high-frequency sounds and to use sensory extinction in noisy areas in order to minimize attention to background noise and hear the main conversation. Although hearing loss poses more of a safety risk when walking in crowded areas or across streets, it does not directly increase fall risk. Screening can be accomplished with cranial nerve testing using a finger rub just outside of the ears or by using a sensory tuning fork (Herdman & Clendaniel, 2014). Taste and smell Changes in taste and smell also may play an indirect role in increasing fall risk in older adults. As we age, we experience a decrease in sense of smell due to decline in sensory nerve endings in the nose. Additionally, a decrease in the number of taste buds on the tongue (which can decline from 40 to 60 years of age) and atrophy of existing taste buds occur with aging. Salty and sweet taste buds atrophy first, followed by bitter and sour taste buds. A decrease in saliva also may occur, along with difficulty swallowing. These sensory changes in some older adults result in a lack of appetite, weight loss, and dehydration. A loss of smell often can result in hygiene issues. Older adults who lose up to 10 pounds of weight unintentionally may be at risk for becoming frail, losing muscle strength, and eventually losing function (Fried et al., 2001). These consequences increase fall risk. Screening for loss of taste and smell can be accomplished through cranial nerve testing. Cognition Cognition is an integration of perceiving, remembering, and thinking. Cognitive skills peak in the third and fourth decades and begin to make small declines in the fifth and sixth. It is not until the typical older adult reaches their seventh decade that noticeable declines in cognition occur. The influence of aging differs on fluid and crystallized intelligence. Fluid intelligence, such as thinking and reasoning, declines at a faster rate than crystallized intelligence, which is more an accumulation of information and vocabulary, and actually may grow as one ages. Memory also changes as we age, with explicit memory (or memory for facts) slowing more than implicit memory (or memory for acquired skills). Short-term memory is impaired more than long-term memory in most older adults who are aging typically. Other aspects of cognition that are negatively affected by the aging process include the following: ● Attention. ● Dual-task abilities. ● Processing speed and robustness. ● Problem solving speed. ● Working memory. ● Word retrieval issues. It is important to understand the role of cognition in postural control. Normal postural control is influenced by the capacity of an individual, the demands of the task, and the strategies used to accomplish the task. As noted previously, cognitive skills Musculoskeletal changes Several age-related declines typically occur in the musculoskeletal system in older adults. This section will cover changes in muscle strength, flexibility, and posture. Muscle strength and age-related changes A decline in muscle strength, especially lower extremity strength, has been identified as a common risk factor for falls. Although muscle strength can be maintained or improved well into advanced age, it does experience age-related declines, with some older adults experiencing up to 40% reduction in lower extremity strength between the ages of 30 and 80 years. This decline starts around age 30 and accelerates after 50 years of age and is most evident in frail older adults and those with a history of falls (Keller & Engelhardt, 2014). The rate of decline in strength is variable among older adults. For example, an 80-year-old man typically has a 12% to 17% loss of knee flexor and extensor strength (Keller & Engelhardt, 2014). Loss of grip strength, in both men and women, also has been linked to fall
such as attention, dual-task abilities, and information processing can be reduced with typical aging (Brustio, 2017). As postural stability demands increase, attentional resources needed to maintain stability also increase. For older adults, this can result in slower reaction times, especially in situations with decreased sensory input and/or dual-tasking, thereby increasing the risk for falls (Shumway-Cook & Woollacott, 2007). Changes in balance strategies Older adults may show delays in balance strategies to keep themselves upright as a result of the various neuromuscular, sensory, and/or cognitive changes already described. The main balance strategies used to maintain upright postural control include ankle, hip, stepping, suspensory, and crossover strategies. Definitions of these strategies can be found in the glossary. These balance strategies may be delayed or ineffective due to increases in latency of distal muscle responses to perturbations, intermittent reversals in normal distal-to-proximal sequence of leg muscle contractions, and/or co-activation of agonist and antagonist muscles for longer periods of time than in young adults. Balance strategies also can be altered by changes in sensory input. When sensory inputs are altered or reduced, older adults can have difficulty with balance, including trouble detecting postural disturbances, delayed reactive balance control, and/or delay in initiation of balance strategies. These changes in balance can be manifested in decreased lateral control of postural stability (multiple steps laterally to maintain balance when perturbed), resulting in an increased risk for lateral falls. During crossover balance reactions, older adults can experience more collisions or failed reactions, as the aging process contributes to a diminishing crossover strategy for reasons such as inactivity or lower extremity muscle weakness (Shumway-Cook & Woollacott, 2007). When balance strategies are inefficient, then falls are the consequence. The aging process also alters balance by negatively influencing the anticipatory and compensatory postural strategies used to maintain stability (Kanekar & Aruin, 2014). Anticipatory reactions, also called anticipatory postural adjustments (APAs), are internally generated by the CNS in anticipation of a known balance disturbance. For example, while standing and donning a shirt overhead, an older adult with normal APAs will self-initiate a forward shift in center of gravity to compensate for the backward shift of weight as they raise their arms above their head. When the balance disturbance is unpredictable, then compensatory postural adjustments (CPAs) occur after the perturbation, resulting in activation of postural muscles in response to sensory feedback signals, which aim to restore postural stability. An example of a CPA would be a lateral step to maintain balance after being pushed at shoulder level while walking. The aging process affects both APAs and CPAs due to sensory losses, decreased muscle strength and power, impaired joint mobility, and changes in sensory integration (Shaffer & Harrison, 2007). risk in a few studies (Szulc, Feyt, & Chapurlat, 2016). Physiologic changes in the muscles of older adults include loss of Type I (slow twitch) and Type II (fast twitch) muscle fibers, a decrease in the number of functional motor units, and muscle fatigue, especially during concentric contractions. Loss of Type II fibers is typically greater than loss of Type I fibers. In addition to loss of strength, muscle endurance and muscle mass in the lower extremities are reduced with aging, more so than in the upper extremities. Lack of activity accelerates a greater loss of strength than of muscle mass (Keller & Engelhardt, 2014), although both muscle strength and mass (to a lesser degree) can be improved in older adults with resistance training. Although resistance training can improve muscle strength and power in older adults, “detraining” can result in swift reversal in strength gains. It is imperative that older adults make strength training a habit for the remainder of their lives to avoid changes in function and to decrease their risk for falls.
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