Neurvous System

The aging of the central nervous system is often portrayed as an irreversible loss of functions and decline in abilities. In the past, scientists reported that we "lose a million neurons every day". Fortunately, that's not correct. The adult brain retains a remarkable plasticity in it's ability to compensate functionally for those losses that do occur. Further, some cognitive abilities, such as wisdom and life experience, are stable or may increase with age.

The weight of your brain peaks around age 20 and then a modest decline occurs with age that is limited to the gray matter (outer surface of the brain) in healthy older people. Older nerve cells may have fewer dendrites (branches) and some may become demyelinated (lose its coating) which can slow the speed of message transmission. Most of these changes do not appear to affect ordinary activities of living.

People often fear cognitive decline in later life more than any other disabling condition. Cognitive ability is crucial to the capacity to live independently. Most of us do not want to be dependent on others as we age. Impairment in cognitive capacity can threaten autonomy and the ability to manage our daily activities.

Most neurological declines occur after age 60 and are not that severe. At age 65, less than 2% of older Americans have cognitive impairment. The incidence of cognitive impairment increases with age so that by age 85, up to 1/3 of older persons have some degree of cognitive impairment.

The cognitive abilities of older adults vary tremendously both within individuals and across age groups. Within individuals some functions may change while others do not. For example, the verbal I.Q. of an individual may be stable while his performance I.Q. declines. Across age groups the average scores may decline with age, however, we can find many older adults who continue to perform at the level of a younger adult.

Many of the abilities in which declines occur can be improved through training and practice in memory techniques, problem-solving skills, and other cognitive strategies. Short-term memory loss is common and determining whether "forgetfulness" is benign or a precursor of dementia is often impossible. The average 70 year old can take up to 4 times longer than a 20 year old in tests involving basic memory skills (Moody, p.406). Older adults are also slower in reaction time than younger adults as is clearly shown by the declines in the speed of information processing.