Alzheimer's disease is a progressive and ultimately fatal form of dementia. It is marked by the formation of unusual structures, sometimes known as amyloid plaques and fibrillary tangles, in the brains of the afflicted. Alzheimer's is the most common form of dementia in older people. Although it cannot be cured, its progression can be slowed.
Two Types
As Medline Plus explains, there are two distinct types of Alzheimer's disease. Late onset Alzheimer's disease is the most common. It affects people over the age of 60, and although there does appear to be a hereditary component, the role of genes is not completely understood. Early-onset Alzheimer's, however, can run in families, and researchers have identified several genes that can lead to this rapidly-progressing form of the disease.
Predisposing Genes
The Genetics Home Reference lists three different genes that have been implicated in the development of early-onset Alzheimer's: APP, PSEN1 and PSEN2. Mutations in these genes can lead to toxic fragments of a protein (also known as A-beta) accumulating in the brain very quickly, which is thought to cause Alzheimer's disease. There is also evidence that people with Down's syndrome are also more likely to develop Alzheimer's. In addition, the National Institute on Aging notes that 40 percent of people with late-onset Alzheimer's have a particular gene called APOE ε4.
Risk Factors
One risk factor of Alzheimer's disease is age; as people get older their likelihood of developing Alzheimer's increases. Chronically high blood pressure, a family history of the disease and a history of head trauma are also associated with an increased risk of Alzheimer's disease.
Early Symptoms
Alzheimer's disease initially manifests itself as mild cognitive and memory impairment. Early symptoms of Alzheimer's include trouble with language (such as forgetting the words for objects), misplaced or lost items, or getting lost while traveling a familiar route. Patients can also lose interest in activities they used to enjoy and struggle to complete actions that require some thinking (balancing a checkbook, for example).
