We still don't understand exactly how Alzheimer's disease damages the brain. Somehow, cells are damaged and eventually die in different areas of the brain. The damaged areas of the brain contain abnormalities called senile plaques and neurofibrillary tangles. The death of brain cells leads to dementia, characterized by memory loss, impaired judgment, loss of independence, and behavioral changes.
Eventually, the person loses their speech as well as their bladder and bowel control. People with Alzheimer's typically die of infections such as pneumonia or other medical problems. Most people live for about 7 years after diagnosis, but some have lived for up to 20 years.
Each case of Alzheimer's usually affects at least two lives: the person with the condition, and the patient's spouse or child, who gradually becomes a full-time caregiver as the disease progresses. Caring for an individual with Alzheimer's can be demanding and stressful. Many caregivers must eventually face the difficult decision of placing their loved one in institutional care.
With Alzheimer's, we look more at risk factors than direct causes.
There may be a genetic factor in Alzheimer's disease, since we know it runs in some families. Researchers have even found a gene that causes a particularly severe form of the disease. If you inherit this gene from only one parent, you have an increased chance of getting Alzheimer's disease, compared to people with the normal gene. Inheriting it from both parents means you'll almost certainly get the disease, and at an earlier age.
Familial autosomal dominant Alzheimer's disease (FAD) is the name given when Alzheimer's disease is clearly passed on from generation to generation in a family. It typically comes on before the age of 60, and the Alzheimer's gene, called APOE e4, turns up in many family members. FAD only explains about 6% of all Alzheimer's disease cases, however.
Another type of Alzheimer's disease, sporadic Alzheimer's disease, also runs in families, but to a much lesser degree. It rarely appears before the age of 70. If one of your parents had Alzheimer's disease but didn't carry the APOE e4 gene, your risk is only slightly higher than that of the general population.
Even if no one in your family has had Alzheimer's, you can still get sporadic Alzheimer's disease. Most researchers believe there are other genes that can make people susceptible to Alzheimer's disease, but genes alone aren't enough - some other trigger has to set off the disease process.
Possible risk factors include:
- head injury: Studies show that people who have suffered concussions are more likely to develop Alzheimer's later on.
- vascular disease: Coexisting small strokes increase the risk and severity of memory problems in Alzheimer's disease.
- obesity: A high waist-to-hip ratio is related to a higher risk of late-onset Alzheimer's disease.
- inflammation: People with arthritis are less likely to get Alzheimer's. It is speculated that the medications used to reduce inflammation in arthritis may have a beneficial effect on an inflammatory process in the brain.
- gender: Women are nearly twice as likely as men to suffer from Alzheimer's.
- education: Research suggests that better educated people are less prone to Alzheimer's. Those who already have the disease do better if they keep mentally active - an unused brain may deteriorate faster.
- toxins (e.g., aluminum): A controversial and unproven theory links aluminum in drinking water to senile plaque formation. Earlier studies hinted at a connection, but not according to recent studies that are larger and better-designed.
- prions: Some scientists speculate that prions, tiny infectious particles made of protein, may be involved in Alzheimer's disease by infecting the brain.