Alzheimer’s disease (AD) is a slowly progressive disease of the brain that is characterized by impairment of memory and eventually by disturbances in reasoning, planning, language, and perception. Many scientists believe that Alzheimer’s disease results from an increase in the production or accumulation of a specific protein (beta-amyloid protein) in the brain that leads to nerve cell death.
The likelihood of having Alzheimer’s disease increases substantially after the age of 70 and may affect around 50% of persons over the age of 85. Nonetheless, Alzheimer’s disease is not a normal part of aging and is not something that inevitably happens in later life. For example, many people live to over 100 years of age and never develop Alzheimer’s disease.
Who develops Alzheimer’s disease?
The main risk factor for Alzheimer’s disease is increased age. As a population ages, the frequency of Alzheimer’s disease continues to increase. Ten percent of people over 65 years of age and 50% of those over 85 years of age have Alzheimer’s disease. Unless new treatments are developed to decrease the likelihood of developing Alzheimer’s disease, the number of individuals with Alzheimer’s disease in the United States is expected to be 14 million by the year 2050.
There are also genetic risk factors for Alzheimer’s disease. Most patients develop Alzheimer’s disease after age 70. However, 2%-5% of patients develop the disease in the fourth or fifth decade of life (40s or 50s). At least half of these early onset patients have inherited gene mutations associated with their Alzheimer’s disease. Moreover, the children of a patient with early onset Alzheimer’s disease who has one of these gene mutations has a 50% risk of developing Alzheimer’s disease.
There is also a genetic risk for late onset cases. A relatively common form of a gene located on chromosome 19 is associated with late onset Alzheimer’s disease. In the majority of Alzheimer’s disease cases, however, no specific genetic risks have yet been identified.
Other risk factors for Alzheimer’s disease include high blood pressure (hypertension), coronary artery disease, diabetes, and possibly elevated blood cholesterol. Individuals who have completed less than eight years of education also have an increased risk for Alzheimer’s disease. These factors increase the risk of Alzheimer’s disease, but by no means do they mean that Alzheimer’s disease is inevitable in persons with these factors.
All patients with Down syndrome will develop the brain changes of Alzheimer’s disease by 40 years of age. This fact was also a clue to the “amyloid hypothesis of Alzheimer’s disease”.
Ten warning signs of Alzheimer’s disease
The Alzheimer’s Association has developed the following list of warning signs that include common symptoms of Alzheimer’s disease. Individuals who exhibit several of these symptoms should see a physician for a complete evaluation.
1. Memory loss
2. Difficulty performing familiar tasks
3. Problems with language
4. Disorientation to time and place
5. Poor or decreased judgment
6. Problems with abstract thinking
7. Misplacing things
8. Changes in mood or behavior
9. Changes in personality
10. Loss of initiative
It is normal for certain kinds of memory, such as the ability to remember lists of words, to decline with normal aging. In fact, normal individuals 50 years of age will recall only about 60% as many items on some kinds of memory tests as individuals 20 years of age. Furthermore, everyone forgets, and every 20 year old is well aware of multiple times he or she couldn’t think of an answer on a test that he or she once knew. Almost no 20 year old worries when he/she forgets something, that he/she has the ‘early stages of Alzheimer’s disease,’ whereas an individual 50 or 60 years of age with a few memory lapses may worry that they have the ‘early stages of Alzheimer’s disease.’