Summary of Development in Adulthood
Development is a lifelong process and adults are just as involved in that process as those in earlier stages of life. The term maturity is related to the periods of young and middle adulthood. It indicates a relatively stable stage. Most changes that occur in this period are motivated by individual responses to environment or task demands (Bertoti, 2004, pg. 54).
The association areas of the brain are responsible for purposeful action. Myelination continues in these areas into adulthood, making it possible for learning to be maximized. I.Q. peaks by about age 30 and reaction time peaks between 20-60 years of age. In addition, synaptic remodeling and growth continue. In general, however, middle adulthood is when the nervous system begins to decline. Brain weight and volume decline linearly with age. A continual loss of neurons (which do not get replaced) begins around age 20 with the speed of nerve conduction decreases beginning around age 30. Short term memory slowly starts to decline around age 30 and becomes more rapid after age 60. Synaptic remodeling and growth continue to occur late into adulthood and allow for plasticity (Bertoti, 2004, pg. 60).
Although development of intersensory associations continue into adulthood, sensory function begins to slowly regress. The changes are very small from young through middle adulthood and suddenly become very evident at about age 45, when reaction times seem to decrease significantly. Skin becomes noticeably dryer and less elastic which affects the precision of cutaneous receptors. Functional impact is rather insignificant because knowledge based on experience helps compensate for motor and sensory decline (Bertoti, 2004 pg. 66).
Visual acuity increases into the 30s, stabilizes in the 40s and 50s and begins to decline. It's common around age 45 to notice farsightedness because the lens of the eye begins to lose some elasticity, making it difficult to focus on objects that are very near. After age 40 it also becomes very hard to adapt quickly from light to dark environments. Also, after age 30, most people begin to develop cataracts (Bertoti, 2004, pg. 72).
In the vestibular system, changes are rather insignificant. The number of sensory fiber cells begins to decrease around age 40, but there are no specific functional consequences (pg. 77).
Physically active adults can maintain and increase their strength. In fact, muscle fibers continue to increase until about age 50. After that, they begin to slowly decline. In men, strength is at its maximum level at about age 30-35 and stays fairly constant until about 50. By age 60 there is a 20% loss of strength. Complex sensorimotor coordination begins to decline around age 30 but is highly variable. After age 40, bone resorption occurs at a higher rate than bone replacement. Cancellous bone loss begins in the 30s and cortical loss in the 40s. A reduction in height may be noticed due to increased vertebral pressure and dehydration of the vertebral discs. Bone loss due to menopause and osteoporosis begins during adulthood as well (Bertoti, 2004, pg. 83).
When working with adults, it's important to bear I mind that their age at the time neurological damage occurs can greatly impact the amount of damage. The effect of damage is closely related to the functional maturity of the damaged area (Bertoti, 2004, pg. 46). In addition, the PTA needs to keep in mind that every patient has a unique developmental timeline and presents with a set of dynamic subsystems. These systems are in fluctuating stages of maturation and aging and may be compromised by pathology (Bertoti, 2004, pg. 84).
Bertoti, D.B., (2004). A Lifetime Approach to the Systems that Produce Human Movement. In M. Biblis & P. Waltner (Eds.), Functional Neurorehabilitation Through the Lifespan. Philadelphia, PA: F.A. Davis.
