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Various dementia types can be caused by medical or psychiatric conditions, among them high fever, vitamin deficiency, head trauma, or depression. These are the so-called “reversible dementias.” Other dementia types are irreversible and—if you’re wondering, “Is dementia hereditary?”—can be caused by family genes.
Let’s look at reversible dementias first. It’s important to see a doctor if you’re experiencing sudden memory-loss symptoms, especially if your health has recently changed.
The following are among the more common reversible causes of memory loss:
- Excess alcohol consumption
- Drug effects and interactions
- Lung problems
- Metabolic disease or abnormalities
- Sleep problems
- Vitamin deficiency
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Some types of dementia are associated with brain damage that is irreversible. These primary dementia types are listed below. In addition to the most common condition, Alzheimer’s disease (AD), several other conditions are also important causes of primary, progressive dementia:
Alzheimer’s Disease (AD). An estimated 5.3 million Americans have Alzheimer’s disease, and the number is increasing rapidly. The devastating neurodegenerative disease is the sixth leading cause of death in the nation, and to date, no treatments are available to prevent or slow its progress. The hallmarks of Alzheimer’s disease are amyloid plaques (accumulations of toxic beta-amyloid proteins that form hard masses in the brain) and neurofibrillary tangles (twisted fibers of abnormal tau protein that accumulate inside the brain’s cells leading to loss of synapses, and eventually cell death). The formation of amyloid plaques and neurofibrillary tangles in the brain are believed to contribute to the degradation of neurons (nerve cells), leading to symptoms of Alzheimer’s disease. People with memory problems who do not have amyloid plaques are unlikely to have AD.
Symptoms of AD steadily worsen, but the rate of decline varies from individual to individual. The average length of survival after diagnosis is four to eight years, but some individuals live as long as 20 years with AD.
Vascular Dementia (VaD). Many conditions that adversely affect the heart can damage the brain and nervous system and increase the risk of memory decline. Cardiovascular and cerebrovascular diseases are the prime actors in VaD, the second most common form of dementia after AD. Causes of VaD include:
- Strokes and transient ischemic attacks: Strokes involve the blockage or rupture of the brain’s blood vessels, which starves brain cells of oxygen and nutrients. Damage may occur from one large stroke; a milder stroke called a transient ischemic attack (TIAs, or “mini-strokes”) with symptoms that disappear within an hour or so; or over time, as the result of a series of imperceptible tiny mini-strokes that progressively destroy small sections of brain cells. Damage that effects regions of the brain involved in learning and memory can lead to vascular dementiaIt’s not possible to reverse the damage caused by a stroke, TIA, or other forms of VaD; however, you may be able to avoid further injury to brain cells by lowering cardiovascular risk factors through simple lifestyle changes.
- Atrial fibrillation (Afib): One in 20 people over age 65, and one in 10 over 80, has Afib, an abnormal heart rhythm in which chaotic pumping actions cause blood to pool, dramatically increasing the risk for brain-damaging strokes and AD. Treatment for Afib usually includes medication, such as drugs to slow the heart rate and blood thinners to reduce the risk of blood clots; cardioversion, which uses electrical pulses or drugs to restore an erratically beating heart to its normal rhythm; and more rarely, catheter ablation, which burns off heart cells that are producing the abnormal rhythm.
Lewy Body Dementia, or Dementia with Lewy bodies (DLB). DLB is the third most common among dementia types, representing between up to 25 percent of dementia cases. This condition is characterized by the buildup of abnormal proteins called Lewy bodies inside neurons in areas of the brain responsible for memory, language, and consciousness.
These same proteins are found in the brains of people with AD and Parkinson’s disease (PD). People with DLB often develop Parkinson’s-like symptoms—including rigid muscles and a shuffling walk—along with other symptoms, such as confusion, trouble thinking and reasoning, hallucinations, and delusions. Although no cure exists for DLB, medications can help control the cognitive symptoms.
Fronto-temporal dementias (FTD). This spectrum of disorders (also known as Pick’s disease) cause atrophy of parts of the frontal and temporal lobes of the brain, which control memory, personality, and language skills. FTD may account for up to 15 percent of all dementias. Symptoms of FTD tend to come on slowly, and typically involve inappropriate behavior, difficulty finding the right words, and personality changes. In its late stages, FTD resembles AD, with significant memory impairment. Although no treatment for FTD exists, antidepressants and antipsychotic drugs may help control the behavioral symptoms.
Parkinson’s disease dementia (PDD). PDD is a form of dementia associated specifically with the movement disorder Parkinson’s disease, which is characterized by muscle rigidity in the limbs, tremors and balance difficulties, abnormal deposits of proteins known as Lewy bodies, and the hallmark plaques and tangles of AD. An estimated 50 to 80 percent of people with Parkinson’s will eventually develop PDD. As with other forms of dementia, PDD gets worse over time.