Summary of Geriatric Development
The main developmental experience during the older adult years is aging. Aging is described as physical, sensory and psychological changes that happen to all elderly people, to some degree, over the course of time (Bertoti, 2004, pg. 55).
Until about age 75, older adults maintain their intellectual ability and can continue to learn well into old age. Their dendrites continue to grow but there is a decrease in the number of neurons as well as a great deal of shrinkage of neurons, especially in the higher-order association areas of the brain. There is a loss of myelin which reduces reaction time, reflex responses and acuity of senses. An example of this is the loss of the knee jerk reaction in most adults over age 70. Motor performance diminishes and, if balance isn't continually challenged and purposeful activities are not maximized, it becomes a "use it or lose it" situation. Balance and functional activities are important areas of focus for a PTA working with aging adults (Bertoti, 2004, pgs. 57 &61).
The somatosensory system is necessary to successfully perform or modify movement. The aging process causes a gradual decline in sensory functioning causing a decrease in the numbers of certain types of sensory neurons, a reduction in the functioning of the rest of the sensory neurons and actual structural and physiological changes within the Central Nervous System (Bertoti, 2004, pg. 66).
The structure of the skin changes with wrinkling, thickness, toughening, differences in the subcutaneous layers, changes in the hair pattern and distribution on the skin's surface. Measurable changes in the threshold to touch stimuli occur with aging as tactile sensitivity decreases. Fine touch, pressure and vibration senses decline along with an up to 30% loss of the sensory fibers that innervate the peripheral receptors. This causes peripheral neuropathy. The most notable areas of reduced touch sensitivity include fingertips, palms and lower extremities (Bertoti, 2004, pg. 67).
Proprioception also declines as the muscle spindles, joint receptors and Golgi tendon organs atrophy with age. This decline negatively impacts the feedback that is usually received by the CNS regarding movement. Arthritic changes can also affect the level of precision in which the joint receptors can detect the position of the joints. These changes have an adverse impact on the efficiency of the proprioceptive system. Elderly adults are forced to compensate for these deficits. The decline in proprioception of the lower extremities increases the fall risk for this population. PTAs will need to use more cues with older adults. This could include verbal, visual, tactile or even biofeedback. Adaptive and/or assistive devices may also be required to provide extra support when somatosensory feedback is no longer reliable (Bertoti, 2004, pg. 67).
Between the ages of 60 and 80 there is a rapid decrease in visual acuity. By age 85, visual acuity drops to 80% of what it was at age 40. Age-related structural changes to the eye cause a decrease in pupil size and less transmission of light to the retina. Macular degeneration and cataracts are common. While a teenager takes about 6 or 7 minutes to adapt from dark to light, older adults need about 45 minutes. Older adults also experience more glare which introduces extraneous light. Depth perception, peripheral vision and contrast sensitivity all decline with age and have a negative impact on safety, balance, postural control and functional independence. In addition, about 10% of older adults have an undiagnosed visual impairment or eye disease. Older adults tend to adapt to these visual declines by relying more on somatosensory input. The PTA can help them adapt their activities and environment, perform tasks and maintain their independence with extra sensory, verbal and tactile cues (Bertoti, 2004, pgs. 72 &73).
Adults over age 70 show a 40% reduction hair cells and a 36% reduction in nerve fibers in the peripheral vestibular system. This causes a decline in their vestibular abilities which negatively affects their postural control. Older adults have a higher incidence of vertigo, dizziness, unsteadiness, increased body sway and balance disorders. This makes it harder for them to navigate in new or unfamiliar environments. The decline in vestibular abilities contributes to falls in older people (Bertoti, 2004, pgs. 77 & 78).
By about age 70, an individual loses about 50% of their strength. Muscle cells degenerate and are replaced by fat. If older adults exercise and engage in moderate weight training, these losses in strength can be minimized. Loss of strength is more noticeable in the lower vs. upper extremities. Weakness and an increase in muscle fatigue are most notes in back, abdominal and quadricep muscles. There is generalized proximal weakness of the pelvic girdle and muscles of the neck. These trunk muscles normally provide stability, so their weakness contributes to less effective balance and equilibrium reactions. Fast twitch muscle fibers are lost at a faster rate than slow twitch, causing slower rates and lower levels of muscle contractions which affect the kinds of movements that can be performed while maintaining postural stability. Flexibility decreases due to changes in collagen, decreased levels of activity and arthritic changes. The most common postural changes for older adults are forward head, rounded shoulders, increased thoracis kyphosis, decreased lumbar lordosis, increased knee flexion and a more posterior hip position. Osteoporosis affects 70% of people over age 70. The PTA needs to focus on encouraging moderate exercise, especially weight-bearing that delivers a mechanical load to the bone. Studies have shown that this can decrease the rate of bone loss (Bertoti, 2004, pg. 84).
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