Mild Cognitive Impairment

Studies of cognitive changes across the life span must distinguish between
normal gradual change in the elderly and change that is associated with disordered
functioning. Studies must also respect the complexity of the human
brain. Morton Hunt notes that cognitive scientists have concluded that
there may be 100 billion neurons in the interior of the brain. Each of these
neurons may be interconnected to hundreds of others by anywhere from
one thousand to ten thousand synapses, or relay points. This may enable the
average healthy person to accumulate five hundred times as much information as is contained in the entire Encyclopedia Britannica, or 100 trillion bits of
information. The circuitry in one human brain is probably sixty times the
complexity of the entire United States telephone system. Given this complexity,
even the daily estimated loss of 100,000 brain cells from the aging
process may leave human beings capable of sound cognitive functioning
well into old age.
“Mild cognitive impairment” is a term used to describe isolated memory
losses without changes in activities of daily living. There is some support for
the theory that mild cognitive impairment represents a transitional stage between
normal aging and Alzheimer’s disease and may be a precursor to Alzheimer’s
disease. A significant proportion of patients with mild cognitive
impairment do not progress to Alzheimer’s disease. One research study followed
a group of mildly cognitively impaired patients and reported they
developed Alzheimer’s disease at a rate of 10 percent to 15 percent per
year, while individuals without mild cognitive impairment developed Alzheimer’s
disease at a rate of 1 percent to 2 percent per year. Individuals who
have a memory problem but do not meet clinical criteria for Alzheimer’s
disease are considered to have mild cognitive impairment with memory
loss. This is an important group for Alzheimer’s disease research because up
to 40 percent of those who are mildly cognitively impaired develop Alzheimer’s
disease within three years. One study supported that those who carried
the gene apolipoprotein E-4 (APOE-4) were more likely to develop
Alzheimer’s disease. Studies involving molecular brain activity have contributed
to understanding normal and abnormal memory activities. Another
study linked poor performance on a memory test that provided cues to help
participants at time of recall indicated a cognitive decline. To date, there
are no treatments to prevent or manage mild cognitive impairment. Therefore,
awareness, understanding the implications, and early identification
are important in management and education about mild cognitive impairment.
Paul Baltes notes that it used to be considered “common knowledge” that
cognitive abilities decline with age, but today this view is highly debatable.
When the effects of disease and injury are separated out in studies of the
healthy elderly, no drastic decline in cognitive ability is found. This conclusion
may be one reason that studies of cognition and aging have begun to
make a distinction regarding intelligence. The distinction is between crystallized
intelligence, involving the accumulation of facts and knowledge,
which holds up with age, and fluid intelligence, which is the rapid processing
of new information, a function that appears particularly associated with
the young and vulnerable to the effects of age or disease. Studies of neurologically
healthy aging adults have revealed no consistent evidence of a reduced
ability to learn. Studies have further shown that very little practice
may be required to improve substantially an elderly person’s ability to perform
some cognitive tasks, reflecting a motivational factor. Studies of mentally
active persons in their eighties have concluded that loss of cognitive ability stemmed more from intellectual apathy or boredom than from actual
physical deterioration.
John Darley and his colleagues concluded that on average, the decline of
intellectual capability with age is slight and probably does not occur before
age seventy-five. When declines do occur, they do not occur equally across
cognitive functions. Vocabulary and verbal skills may actually improve with
age, whereas skills involving spatial visualization and deductive reasoning
are more likely to diminish. In general, verbal skills and accumulated knowledge
are maintained with aging, while tasks that require quick responses are
more susceptible to aging.