Alzheimer's Disease and other Dementias
The Other Dementias
Dementia is the loss of cognitive functioning—thinking, remembering, and reasoning—and behavioral abilities to such an extent that it interferes with a person’s daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a person’s functioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living.
Many conditions and diseases cause dementia. The most common cause of dementia in older people is Alzheimer’s disease. Other causes include different kinds of brain changes that lead to vascular dementia, Lewy body dementia, and frontotemporal disorders.
In addition, some people have mixed dementia—a combination of two or more disorders, at least one of which is dementia. A number of combinations are possible. For example, some people have Alzheimer’s disease and vascular dementia at the same time.
Other causes of dementia include Huntington’s disease, Creutzfeldt-Jakob disease, head injury, and HIV. In addition, some conditions that cause dementia, such as normal pressure hydrocephalus, thyroid problems, and vitamin B deficiency, can be reversed with appropriate treatment. For an overview of all types of dementia, see the booklet The Dementias: Hope Through Research. For more information about these conditions, visit the National Institute of Neurological Disorders and Stroke.
Vascular dementia, considered the second most common form of dementia after Alzheimer’s disease, results from injuries to the vessels supplying blood to the brain, often after a stroke or series of strokes. Vascular dementia and vascular cognitive impairment arise as a result of risk factors that similarly increase the risk for cerebrovascular disease (stroke), including atrial fibrillation, hypertension, diabetes, and high cholesterol. The symptoms of vascular dementia can be similar to those of Alzheimer’s, and both conditions can occur at the same time. Symptoms of vascular dementia can begin suddenly and worsen or improve during one’s lifetime.
Some types of vascular dementia include:
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)
Subcortical vascular dementia (Binswanger’s disease)
Research has shown that Alzheimer’s and vascular disease-associated cognitive impairment are closely intertwined. For example, a large proportion of people diagnosed with Alzheimer’s also have brain damage caused by vascular disease. In addition, several studies have found that many of the major risk factors for vascular disease may also be risk factors for Alzheimer’s.
The overlap between these two types of dementia may be important because medications and lifestyle changes known to help prevent vascular disease, such as controlling high blood pressure, lowering cholesterol, and engaging in physical activity, may also help prevent Alzheimer’s disease.