According to the National Institute of Neurological Disorders and Stroke, dementia is common in older people. Elderly dementia--symptoms of cognitive and behavioral impairment--can be caused by some medications, health conditions such as lung disease, and diseases. Merck Manual notes that the most common cause is Alzheimer's disease, which accounts for 75 percent of dementia cases. This overview is on Alzheimer's-related dementia as well as other causes of dementia.
Alzheimer's Disease
Scientists have yet to pinpoint the specific cause of Alzheimer's disease but it results in a loss of functioning brain cells, or neurons. The Mayo Clinic explains that plaques, bunches of beta-amyloid protein, and tangles, groups of tau protein, collect in areas of the brain that deal with memory and language.
Although plaques and tangles are part of normal aging, elderly individuals with Alzheimer's have much more of both. The National Institute of Neurological Disorders and Stroke adds that researchers aren't yet sure if plaques and tangles themselves cause dementia or if the unknown process that initially leads to Alzheimer's is the real factor.
Stroke
Stroke and other conditions that affect the cardiovascular system can cause dementia by impairing the delivery of oxygen to the brain. This type of dementia is known as vascular dementia, and according to the Merck Manual, it is the second most common type after Alzheimer's-related dementia.
Depending on what part of the brain is affected by the stroke or vascular disorder dementia, the dementia may be more or less severe. For example, a patient that suffers many small strokes in specific areas in the brain may experience language deficits but not necessarily memory problems.
Lewy Bodies
Structures called Lewy bodies can also cause dementia. Lewy bodies are abnormalities that contain a protein called alpha-synuclein in the neurons. According to the National Institute of Neurological Disorders and Stroke, Lewy bodies usually appear in the brain's cortex.
Similar to plaques and tangles, they are sometimes found in patients with Alzheimer's disease. The Mayo Clinic notes that dementias caused by Lewy bodies involve problems with confusion and lucid thinking. More so than Alzheimer's disease, dementia caused by Lewy bodies can result in hallucinations.
Creutzfeldt-Jakob Disease
Dementia caused by Creutzfeldt-Jakob disease usually appears in individuals over the age of 60, notes the National Institute of Neurological Disorders and Stroke. Abnormal proteins called prions cause this type of dementia. The prions destroy neurons throughout the brain giving it a sponge-like appearance. Widespread neuronal death damages memory, changes personality and affects cognition.
