Aging and Cognitive Function
How does aging affect the nervous system?
Almost all of us become aware of changes in memory and thinking (cognition) as we get older. We begin to have difficulty recalling names of persons and places, note that mental processing has slowed and learning is more difficult, and find that certain visuomotor functions (motor skills involving vision, such as eye-hand coordination) are also slower.
When should memory loss become a concern?
This question is difficult to answer because memory loss can be influenced by many factors. Changes in a person's physical health can bring about temporary cognitive decline ("delirium" or encephalopathy) and psychosocial issues -- such as loss of friends or loved ones -- can lead to depression, which may mimic the effects of dementia.
Formal definitions of dementia require not only memory loss, but other signs of cognitive decline such as:
- Inability to express or understand language (aphasia)
- Inability to carry out specific skilled motor actions (apraxia)
- Impairment in visual or auditory perception (agnosia)
Common definitions of dementia require that these factors interfere sufficiently with social or occupational functioning and be sustained and progressive.
What is the role of the physician?
Patients or families who believe that the normal effects of aging have been exceeded should consult a physician, often a family practitioner, internist, geriatrician or neurologist. The evaluation that can be expected should include a careful and thorough history and examination with neurological assessment, involving some screening tests of cognitive function designed to confirm the presence or absence of dementia. Additional laboratory studies would usually involve blood work and a scan of the brain to look for conditions other than the most common form of dementia, Alzheimer's disease.
How common are dementia and Alzheimer's disease?
It is generally acknowledged that dementia doubles in frequency every 5 years from the age of 65. Estimates suggest that 5 percent of those age 65 have dementia and for those in the 85 to 90 year range, estimates as high as 50 percent have been suggested. Of those who have dementia, from 50 to 75 percent are thought to suffer from Alzheimer's disease (probably closer to the latter figure).
Thus, dementia -- and particularly Alzheimer's disease -- represent very significant public health problems, since the percentage of the population in this age group is rapidly increasing. It is currently estimated that some 4.5 million adults suffer from Alzheimer's disease and by the year 2030, this number may easily double or triple. Current estimates of the total cost for health care to this segment of the United States population come close to 100 billion dollars annually.
What can be done about Alzheimer's disease?
At this point in time, Alzheimer's disease cannot be cured but it can be effectively treated. Current symptomatic treatment targets the cognitive and the behavioral changes brought about by this disease. Five drugs are currently available for cognitive impairment:
- Tacrine (Cognex)
- Donepezil (Aricept)
- Rivastigmine (Exelon)
- Galantamine (Reminyl)
- Memantine (Namenda)
The first four medications increase the neurotransmitter acetylcholine, which is deficient in patients with Alzheimer's disease. Side effects are not uncommon. Cognex is rarely prescribed now because of its relative toxicity. Namenda acts on a different chemical system and is commonly used together with one of the other medications.
Of equal or perhaps even greater importance are efforts to control the behavioral aspects of dementia, including:
- apathy
- agitation
- anxiety or irritability
- wandering
- depression
- lack of inhibition
A variety of non-medication approaches are available; the most important of these include:
- Educating the caregiver about the disease.
- Providing the patient with a stable and calm environment.
- Offering the patient outlets for energy expression.
- Promoting normal sleep patterns. Medications may be necessary for sleep and for the not uncommon symptoms of uncontrollable agitation, violence, or hallucinations.