Dementia is a decline in cognitive ability that interferes with the activities of daily living, and is typically associated with aging. There are many causes of dementia, and a patient may have more than one disorder contributing to the cognitive decline. Frequent causes of dementia include:
Affecting more than 5 million persons in the United States and 13 million persons worldwide, Alzheimer’s disease is associated with the accumulation of amyloid plaques and neurofibrillary tangles in the brain, with associated damage to brain cells (neurons). These changes begin to occur many years prior to the appearance of symptoms. Alzheimer’s disease most frequently becomes evident in persons in their late 60’s or older, but "early onset" Alzheimer's disease can arise earlier in life. Alzheimer's patients typically have difficulty storing new memories, or remembering conversations or questions for even a few moments. Patients typically have diminished capacity to focus or perform complex tasks, and become disoriented as to time and place. Early symptoms can also include difficulty with financial tasks, such as balancing a checkbook, or problems in finding words. Later symptoms may include wandering, personality changes, hallucinations, fear, and loss of the ability to recognize people or things. However, many of these symptoms can also be caused by other factors, and thus misdiagnosis occurs in more than 20% of cases. More information about Alzheimer’s disease can be found at www.alz.org.
Lewy body disease
This form of dementia is caused by the accumulation of abnormal proteins called Lewy bodies, composed of the protein synuclein. Lewy body disease has many overlapping symptoms with Alzheimer’s disease and is often misdiagnosed. In addition, more than 30% of persons who have Alzheimer’s disease as a primary cause of symptoms also have Lewy body disease. Commonalities between Lewy body disease and Alzheimer’s disease include problems with memory and reasoning, as well as planning, and processing of visual and spatial information. Lewy body disease has some differences from Alzheimer’s disease, in that: 1) problems with attention, working memory, and visuospatial perception may be more pronounced in Lewy body disease, and memory loss may appear later than in Alzheimer’s disease; 2) symptoms often fluctuate, creating good times or days and then very symptomatic times or days; 3) Parkinson’s-like challenges may be present, including muscle stiffness or rigidity (and risk for falling and balance), fluctuations in blood pressure (which can cause dizziness), and digestive irregularities such as constipation, 4) hallucinations may occur, as in confusing shadows with various objects or misinterpreting items seen, and 5) there may be “acting out” in REM sleep. As in Parkinson’s, depression is common. More information about Lewy body disease can be found at www.lbda.org.
Cerebrovascular disease and Stroke
Cerebrovascular disease is a category of disorders involving abnormal blood flow in the brain, including stroke, which occurs when blood supply to the brain is diminished due to narrowed, blocked, or leaking blood vessels. A Transient Ischemic Attack (TIA or “mini-stroke”) is a temporary reduction of blood flow to the brain that can cause lasting cognitive effects. Cerebrovascular disease can cause a slowing of thinking, or symptoms that mimic those of Alzheimer’s disease, where the symptoms depend on the brain region affected. Cerebrovascular disease can co-exist with other forms of dementia, and may be a risk factor for Alzheimer’s disease.
Frontotemporal dementia (FTD)
FTD refers to a collection of disorders affecting neurons in the frontal lobes of the brain, including 1) the frontal or behavioral variant, which involves diminished capacity for complex thought, changes in personality, and loss of inhibition; 2) semantic dementia, which affects finding and use of words; and 3) non-fluent progressive aphasia, which affects the ability to produce speech and, ultimately, written expression. More information on FTD can be found at www.theaftd.org
Parkinson's disease dementia (PDD)
Parkinson's disease is usually associated with its effect on movement, but approximately 30% of persons who have Parkinson’s disease also develop dementia. This has been attributed to Lewy bodies and in some cases to co-existing Alzheimer’s disease. However, in these persons, the motor symptoms of Parkinson’s disease typically appear first, leading to a diagnosis of Parkinson’s before dementia develops.
Depression and Stress
Depression, stress, and lack of sleep, can all cause diminished capacity to think clearly and remember things. Conversely, dementia can also cause depression, but depression can be caused by many other factors.
Abnormal thyroid levels
Low thyroid function can cause difficulty in finding words and thinking clearly. This can occur in the elderly even if thyroid test results are not numerically out of the normal range (“subclinical”). Overactive thyroid can also cause cognitive difficulties, including paranoia. Assessment of dementia typically includes testing for abnormal thyroid.
B12 or other deficiencies
Deficiencies in certain vitamins and minerals can cause cognitive dysfunction. Low sodium levels can also cause confusion, and if severe, paranoia. Assessment of dementia typically includes blood tests.
Infections can cause significant flare-ups of symptoms in elderly patients with dementia.