Alzheimer's Disease: Overview and Risk Factors
Alzheimer's disease is the most common form of dementia in the United States, affecting about 5 million Americans.
Its causes have not been fully elucidated. However, it is known that affected patients accumulate abnormal deposits in their brains, called beta amyloid plaques, as well as disorganized protein fibers, called neurofibrillary tangles. Alzheimer's disease is also associated with the death of certain brain cells that normally produce a neurotransmitter called acetylcholine, and the main part of the brain- the cerebral cortex- diminishes in size.
Early stages of the disease can be mild, and may not appear any different from the typical signs of aging. However, advanced disease is generally associated with severe memory loss and changes in mental abilities, personality, and behavior. The affected person may show confusion, difficulty with language, and difficulty concentrating, and may even experience hallucinations.
Although Alzheimer's disease does not directly cause death, life expectancy after diagnosis is decreased by as much as 50 percent. Patients often die from infections, such as pneumonia or urinary tract infections.
Older persons, women, and African-Americans tend to develop Alzheimer's at higher rates. Evidence suggests that Alzheimer's disease is associated with the following:
- Older age: Age is clearly an important factor in the development of this disease. Few people younger than 60 have the disease, but more than half of people older than 90 are affected. As the American population continues to live longer, scientists estimate that the number of patients with Alzheimer's disease will triple by 2050.
- Family history: The chance of developing the disease is increased by 10 to 30 percent in individuals who have an affected first-degree relative. Risk is particularly high if the condition was known to start at a young age. A specific gene, called apolipoprotein E epsilon 4, appears to be involved, and other genes may also contribute.
- Elevated cholesterol: High levels of low-density (LDL, or "bad") cholesterol are associated with an increased risk. In a study of more than 1,000 postmenopausal women, individuals with the highest LDL cholesterol levels had nearly double the risk of developing Alzheimer's disease, compared with individuals with lower LDL levels.
- Existing medical conditions: Several disorders have been associated with a greater risk of developing Alzheimer's disease, including obesity, diabetes, "pre-diabetes," hypertension, and cardiovascular disease.
- Smoking and excessive alcohol use may increase the risk.
Other factors that may be associated with the development of Alzheimer's disease include a history of depression and a history of severe head injury.
Alzheimer's Disease: Diagnosis and Treatment
There is no definitive test for Alzheimer's disease. It is usually diagnosed based on information from the patient and family.
Doctors also conduct a mental status examination, using a series of questions that are designed to test for short- and long-term memory, the ability to learn and remember new information, mental functioning, and reasoning ability. This may include writing a full sentence, remembering and repeating a short list of words, and reciting the day and date.
Blood tests, CT scanning, MRI, or other tests may be needed to check for other diseases that may appear similar to Alzheimer's.
There is no known cure for Alzheimer's disease. Treatment is primarily based on controlling the symptoms and ensuring patient safety.
Certain drugs (e.g., tacrine, donepezil, and memantine) may slow the progressive loss of memory and mental function. However, these drugs may have only a small effect and are not effective in all patients.
Ginkgo biloba may provide a modest benefit in patients with early, mild disease.
Additionally, mental and physical exercise may help slow the disease process.
Patient safety is an important aspect of treatment. As the disease progresses, patients should avoid driving. Eventually, most daily activities should be monitored, particularly cooking and traveling outside the house. In most cases, nursing home admittance or full-time home care ultimately becomes necessary.
Alzheimer's Disease: Nutritional Considerations
Evidence suggests that nutrition may influence the risk of Alzheimer's disease. The following factors are under study for their role in reducing risk:
- A cholesterol-free diet low in saturated fats and trans fats: Studies have shown that people who eat high amounts of saturated fats, which primarily come from animal products, and trans fats (partially hydrogenated oils found in many snack foods) may have an increased risk of developing Alzheimer's disease. These fats tend to increase the amount of cholesterol in the blood and may increase the risk of Alzheimer's disease. The best approach to reducing cholesterol is to avoid animal products and keep vegetable oils to a minimum.
- A diet high in certain antioxidants: Two studies found that greater intakes of foods high in either vitamin E or vitamin C may lower the risk for Alzheimer's disease. Good sources of vitamin C include citrus fruits, kiwi, melons, and many vegetables. Good sources of vitamin E include wheat germ, peanuts, and sunflower seeds. Antioxidant supplements may also be beneficial, but they do not take the place of fruits, vegetables, beans, and whole grains.
- Vitamins: Adequate intake of folate, vitamin B6, and vitamin B12 may decrease risk.
- Avoidance of dietary or environmental exposure to aluminum: Although there is no conclusive evidence of a role of aluminum as a direct cause of Alzheimer's disease, epidemiological studies have found an association between aluminum in drinking water and Alzheimer's disease.
Aluminum has caused neurotoxic effects in individuals who have been exposed to high levels (e.g., occupational exposure, dialysis, aluminum-containing medications). Aluminum is found in some common antacid products and in cookware. Some evidence suggests that patients with Alzheimer's disease have increased absorption of aluminum even when they are on normal diets.
- Avoidance of excess iron: Iron accumulates in the brain during aging, and some evidence exists that iron may contribute to the disease. Some practitioners use a treatment, called chelation, to remove excess aluminum, iron, and copper from the body.
- Nutritional support: In cases of advanced Alzheimer's disease, enriched and energy-dense foods may be necessary to prevent weight loss.