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 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
of vestibular hypofunction and disease of the vestibular system with advancing age. One unwanted consequence is a decrease in dynamic visual acuity, making it difficult for older adults to maintain visual gaze stability on objects as they move in their environment. For example, while walking or driving. Loss of dynamic visual acuity can result in “dizziness” or even motion sensitivity during activities that involve head movement and very few activities do not involve head movement. Therefore, the older adult limits head movement and avoids motions that require faster head motions. For example, they may walk more slowly, with a wider base of support, stop turning their head during gait, lie down in bed more slowly, and limit larger head motions that typically occur with bending over, reaching for objects on high shelves, or turning quickly to look over their shoulder while driving. Although vestibular assessment is a newer area of rehabilitation for many occupational and physical therapists, it is important to recognize signs of avoidance behavior. Lack of head turning, slow gait speed, and/or adapting activities of daily living (ADLs) to avoid head movement are potential signs that should trigger the need a full vestibular evaluation, or a referral to a specialist for a full vestibular assessment. A detailed description of aging and postural control can be found in the textbook Motor Control: Translating Research into Clinical Practice , by Shumway-Cook and Woollacott (2007), which also includes changes in the neurologic and musculoskeletal systems. Sensory changes with a lesser effect on fall risk The previously discussed sensory changes that influence fall risk in older adults are more common, but are not the only sensory modalities affected by the aging process. The following section will explore sensory changes that may influence fall risk to a lesser degree. Hearing Although loss of hearing may be one of the most common complaints about aging of an older adult or their family, hearing loss has a minimal effect on fall risk. Presbycusis, or hearing loss typically due to noise exposure, occurs in the seventh and eighth decades of life, which is later than most other sensory changes. Age-related hearing loss is typically a result of inner ear bone deterioration, sensory neural cell deterioration, and/or 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
Page 63
EliteLearning.com/Physical-Therapy
Powered by FlippingBook