Alzheimer's Disease : Diagnosing, Part 2. Causes of Dementia

by National Institute on Aging

(Page 10 of 16)

Working with these participants has allowed the research teams to explore several exciting ideas. For example, the Religious Orders Study team recently worked with their participants to examine a "use-it-or-lose-it" brainpower hypothesis. At an initial evaluation, the researchers asked more than 700 priests and nuns about the amount of time they spent in seven common activities that involve significant information processing - watching television; listening to the radio; reading newspapers or magazines; reading books; playing cards, checkers, and puzzle games; and going to museums. After tracking the participants for 4 1/2 years, the researchers found that, on average, the risk of developing AD was 47 percent lower in those who did these activities most frequently than in those who did them least frequently. The reasons for this finding aren't entirely clear yet, but it may be that mentally stimulating activities protect the brain in some way. Or, perhaps some other mechanism may be at work that strengthens information processing skills to compensate for age-related declines in other cognitive areas.

The Nun Study has one particularly rich treasure trove to work with - the autobiographies written by the nuns when they entered the order. These personal records provide basic information on the nuns' early lives and families and are an objective measure of each woman's ability to think, remember, and present ideas in writing. Study investigators have found a fascinating link between their early writing skills and later cognitive abilities. The researchers performed an analysis of the autobiographies to determine the grammatical complexity and the "density" of ideas in each. They then examined brain tissue from nuns who had died. The investigators found that most of the nuns whose brain tissue showed significant signs of AD had written autobiographies with low grammatical complexity and idea density. Though the reasons for this link aren't fully understood, a higher linguistic ability early in life may provide some protection against the influences that lead to Alzheimer's Disease.

Causes of Dementia

Dementia is the loss of cognitive functioning - thinking, remembering, and reasoning - to such an extent that it interferes with a person's daily life and activities. It is not a disease itself, but a group of symptoms that often accompanies a disease or condition. Some dementias are treatable or curable; others are less responsive to treatment.

Current Tools For Diagnosing Alzheimer's Disease

A definitive diagnosis of Alzheimer's disease is still only possible after death, during an autopsy, when the plaques and tangles can actually be seen. But with the tools now available, experienced physicians can be pretty confident about making an accurate diagnosis in a living person. Here's how they do it.

They take a detailed patient history, including: a description of how and when symptoms developed, a description of the patient's and his or her family's overall medical condition and history, an assessment of the patient's emotional state and living environment.

They get information from family members or close friends: people close to the patient can provide valuable insights into how behavior and personality have changed; many times, family and friends know something is wrong even before changes are evident on tests.

They conduct physical and neurological examinations and laboratory tests: blood and other medical tests help determine neurological functioning and identify possible non-AD causes of dementia.

They do a computerized tomography (CT) scan or a magnetic resonance imaging (MRI) test: brain scans like these can detect strokes or tumors or can reveal changes in the brain's structure and function that indicate early AD.

They conduct neuropsychological testing: Q&A tests or other tasks that measure memory, language skills, ability to do arithmetic, and other abilities related to brain functioning help indicate what kind of cognitive changes are occurring.

Criteria for "Probable" Alzheimer's Disease

Because no simple and reliable biological test for Alzheimer's Disease is available, the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Association together established criteria to help physicians diagnose AD. These criteria also help physicians distinguish between AD and other forms of dementia. "Probable" Alzheimer's disease is determined when a person has: dementia confirmed by clinical and neuropsychological examination, progressive worsening of memory and other mental functioning, no disturbances of consciousness (no "blacking out"), symptoms beginning between ages 40 and 90, no other disorders that might account for the dementia.

As they get older, some people develop a memory deficit greater than that expected for their age. However, other aspects of cognition are not affected, so these people do not meet all the accepted criteria for AD. Thus, they are said to have "mild cognitive impairment" (MCI). About 40 percent of these individuals will develop Alzheimer's Disease within 3 years. Others, however, do not seem to progress to AD, at least in the time frame studied thus far (up to approximately 6 years). Understanding more about the characteristics and development of MCI is essential in helping clinicians diagnose early stages of AD.

About the Author

www.nia.nih.gov
NIA, one of the 27 Institutes and Centers of NIH, leads a broad scientific effort to understand the nature of aging and to extend the healthy, active years of life. In 1974, Congress granted authority to form NIA to provide leadership in aging research, training, health information dissemination, and other programs relevant to aging and older people.