According to the World Health Organization, an estimated 47.5 million people worldwide are living with dementia and 10 million new cases are diagnosed each year. Caused by a variety of different mechanisms and illnesses, dementia is a general term used to describe impairment in memory, thinking and decision making. Dementia disorders are usually chronic and progressive and affect reasoning, cognitive skills, behavior, and everyday abilities. These changes can become overwhelming for the patient, their family and especially those who provide care.
Understanding the different types of dementia and how they affect the elderly is helpful in recognizing symptoms, making treatment decisions and making plans for care. Dementia disorders can be classified in many different ways; grouping disorders by common features, such as how they are caused and what parts of the brain are affected. It is important to note that mixed forms of dementia are possible, meaning that different forms co-exist. And, although the condition primarily affects individuals over age 65, dementia is not a normal part of getting older.
Dementia Classifications
Cortical Dementia
Damage primarily affects the brain's cortex, or outer layer. It tends to cause problems with memory, language, thinking, and social behavior.
Subcortical Dementia
Affects parts of the brain below the cortex. Subcortical types tend to cause changes in emotions and movement in addition to problems with memory.
Progressive Dementia
Most types of dementia progress, meaning they inevitably get worse over time. There is no set path that every patient follows, nor does progressive mean that changes in cognitive and physical functioning decline at the same pace. Progressive dementias will eventually interfere with more and more cognitive abilities and daily activities.
Primary Dementia
Primary, in medical language, refers to the place of origin. It follows, then, that primary dementia indicates that the diagnosis of impairment is not a result of any other disease. Alzheimer's disease (AD) is a primary type.
Secondary Dementia
Secondary dementia indicates the condition occurs as a result of another physical disease or injury. For example, a person who has a brain tumor or is diagnosed with Parkinson's disease can develop dementia in the progression of the disease. Secondary dementias are caused by changes related to the patient's original diagnosis.
Some types fit into more than one of these classifications. For example, AD is considered both progressive and cortical.
Alzheimer's Disease
Alzheimer's disease (AD) is the most common cause of dementia in people aged 65 and older. Experts believe that up to 6.2 million people in the United States are currently living with the disease. This means one in ten people over the age of 65 has AD. Hundreds of thousands of Americans are diagnosed with AD each year and it is the sixth leading cause of death in the United States.
In most people, symptoms appear after age 60. Alzheimer's usually causes a gradual decline in cognitive abilities, typically over a span of 7 to 10 years. Nearly all brain functions, including memory, movement, language, judgment, behavior, and abstract thinking, are eventually affected.
AD is characterized by two abnormalities in the brain: amyloid plaques and neurofibrillary tangles. Amyloid plaques found in the tissue between nerve cells are unusual clumps of a protein called beta amyloid along with degenerating bits of neurons and other cells. Neurofibrillary tangles are composed of tau proteins that accumulate within nerve cells in the brain.
Symptoms of AD
In the early stages of dementia, people may experience memory impairment, lapses of judgment, and subtle changes in personality. As the disorder progresses, memory and language problems worsen and people begin to have difficulty performing activities of daily living, such as balancing a checkbook or remembering to take medications. They also may have difficulty navigating an unfamiliar route, become disoriented about places and times, suffer from delusions (such as the idea that someone is stealing from them or that their spouse is being unfaithful), or become short-tempered and hostile.
During the late stages, elders begin to lose the ability to control motor functions. They may have difficulty swallowing and lose bowel and bladder control. They eventually lose the ability to recognize family members and to speak. It also begins to severely affect the person's emotions and behavior. Many people eventually develop behavioral symptoms such as aggression, agitation, depression, sleeplessness, paranoia or delusions.
How Long Do People with Alzheimer's Live?
On average, individuals live for 8 to 10 years after they are diagnosed. However, some people may live as long as 20 years. The true cause of death in these patients is often aspiration pneumonia because people with severe Alzheimer's lose the ability to swallow in the final stages of the disease.
Vascular Dementia
This type is the second most common cause after AD, accounting for an estimated 20 to 30 percent of all dementias. It is caused by brain damage from cerebrovascular or cardiovascular problems (usually strokes). It also may result from genetic diseases, endocarditis (infection of a heart valve), or amyloid angiopathy (a process in which amyloid protein builds up in the brain's blood vessels, sometimes causing hemorrhagic or "bleeding" strokes). In many cases, it may coexist with AD.
Symptoms of Vascular Dementia
Affected individuals frequently wander at night and often have other problems commonly found in people who have had a stroke, including depression and incontinence.
Symptoms often begin suddenly, frequently after a stroke. Those at the highest risk have a history of high blood pressure, vascular disease, or previous strokes or heart attacks. Vascular dementia may or may not get worse with time, depending on whether the person has additional strokes. When the disease does get worse, it often progresses in steps or stages, with sudden changes in ability.
When coupled with brain damage to the mid-brain regions, gradual, progressive cognitive impairment can occur that often strongly resembles AD. Unlike elders with AD, though, these patients often maintain their personality and normal levels of emotional responsiveness until the later stages of the disease.
Types of Vascular Dementia
There are several types, which vary slightly in their causes and symptoms.
Multi-infarct dementia (MID): This type is caused by numerous small strokes in the brain. MID typically includes multiple damaged areas, called infarcts, along with extensive lesions in the white matter, or nerve fibers, of the brain.
Single-Infarct Dementia: Although not all strokes cause cognitive problems, in some cases a single massive stroke can damage a specific area of the brain enough to cause dementia. This is more common when the stroke takes place on the left side (hemisphere) of the brain and/or when it involves the hippocampus, a brain structure important for memory.
Binswanger's Disease: This is a rare type characterized by damage to small blood vessels in the white matter of the brain (white matter is found in the inner layers of the brain and contains many nerve fibers coated with a whitish, fatty substance called myelin). Binswanger's leads to brain lesions, loss of memory, disordered cognition, and mood changes.
People with Binswager's often show signs of abnormal blood pressure, stroke, blood abnormalities, disease of the large blood vessels in the neck, and/or disease of the heart valves. Other prominent features include urinary incontinence, difficulty walking, clumsiness, slowness, lack of facial expression, and speech difficulty. These symptoms, which usually begin after the age of 60, are not always present in all people and may sometimes appear only temporarily. Treatment of Binswanger's is symptomatic, and may include the use of medications to control high blood pressure, depression, heart arrhythmias, and low blood pressure. The disorder often includes episodes of partial recovery.
CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy): This type is linked to a rare hereditary disorder and is linked to abnormalities of a specific gene, Notch3, which is located on chromosome 19. This condition causes MID as well as stroke, migraine with aura, and mood disorders. The first symptoms usually appear in people who are in their twenties, thirties or forties and affected individuals often die by age 65. Researchers believe most people with CADASIL go undiagnosed, and the actual prevalence of the disease is not yet known.
Other vascular causes include vasculitis, an inflammation of the blood vessel system; profound hypotension (low blood pressure); and lesions caused by brain hemorrhage. The autoimmune disease lupus erythematosus and the inflammatory disease temporal arteritis can also damage blood vessels in a way that leads to a vascular dementia diagnosis.
Lewy Body Dementia
Lewy Body Dementia (LBD) usually occurs sporadically in people with no known family history of the disease. However, rare familial cases have occasionally been reported. In LBD, cells die in the brain's cortex, or outer layer, and in a part of the mid-brain called the substantia nigra which plays an important role in movement, learning, reward-seeking and addiction.
Many of the remaining nerve cells in the substantia nigra contain abnormal structures called Lewy bodies that are the hallmark of the disease. Lewy bodies may also appear in the brain's cortex, or outer layer.
Lewy bodies contain a protein called alpha-synuclein that has been linked to Parkinson's disease and several other disorders. Researchers, who sometimes refer to these disorders collectively as "synucleinopathies," do not yet know why this protein accumulates inside nerve cells in LBD.
Symptoms of Lewy Body Dementia
The symptoms of LBD overlap with AD in many ways, and may include memory impairment, poor judgment and confusion. However, LBD typically also includes visual hallucinations, parkinsonian symptoms such as a shuffling gait and flexed posture, and day-to-day fluctuations in the severity of symptoms. People with LBD live an average of 7 years after symptoms begin.
There is no cure for LBD, and treatments are aimed at controlling the parkinsonian and psychiatric symptoms of the disorder. People sometimes respond dramatically to treatment with antiparkinsonian drugs and/or cholinesterase inhibitors, such as those used for AD. Some studies indicate that neuroleptic drugs, such as clozapine and olanzapine, also can reduce the psychiatric symptoms of this disease. But neuroleptic drugs may cause severe adverse reactions, so other therapies should be tried first and people using these drugs should be closely monitored.
Lewy bodies are often found in the brains of people with Parkinson's disease and AD. These findings suggest that either LBD is related to these other disorders or that the diseases sometimes coexist in the same person.
Frontotemporal Dementia (FTD)
Sometimes called frontal lobe dementia, FTD describes a group of diseases characterized by degeneration of nerve cells—especially those in the frontal and temporal lobes of the brain. Unlike AD, FTD usually does not include the formation of amyloid plaques. In many people with FTD, there is an abnormal form of tau protein in the brain, which accumulates into neurofibrillary tangles. This disrupts normal cell activities and may cause the cells to die.
Experts believe FTD accounts for two to ten percent of all cases of dementia. Symptoms of FTD usually appear between the ages of 40 and 65. In many cases, those affected have a family history of dementia, suggesting that a strong genetic factor is at play in the disease. The duration of FTD varies, with some patients declining rapidly over two to three years and others showing only minimal changes for many years. People with FTD live with the disease for an average of five to ten years after diagnosis.
Symptoms of FTD
Because structures found in the frontal and temporal lobes of the brain control judgment and social behavior, people with FTD often have problems maintaining normal interactions with others and following social conventions. They may steal or exhibit impolite and socially inappropriate behavior, and they may neglect their normal responsibilities. Other common symptoms include loss of speech and language abilities, compulsive or repetitive behavior, increased appetite, and motor problems such as stiffness and balance problems. Memory loss may occur, although it typically appears later on in the disease.
Types of FTD
There are a few different types of FTD, each with their own characteristics and symptoms:
Pick's disease: In this type, vertain nerve cells become abnormal and swollen before they die. These swollen or ballooned neurons are one hallmark of the disease. The brains of people with Pick's also have abnormal structures called Pick bodies, composed largely of the protein tau, inside the neurons. The cause of Pick's is unknown, but it runs in some families and thus it is probably due at least in part to a faulty gene or genes. The disease usually begins after age 50 and causes changes in personality and behavior that gradually worsen over time. The symptoms of Pick's are very similar to those of AD and may include inappropriate social behavior, loss of mental flexibility, language problems, and difficulty with thinking and concentration. There is currently no way to slow the progressive degeneration found in Pick's. However, medication may be helpful in reducing aggression and other behavioral problems, and in treating depression.
FTD with Parkinsonism: In some cases, familial FTD is linked to a mutation in the tau gene. This disorder, called FTD with parkinsonism linked to chromosome 17 (FTDP-17), is much like other types of FTD, but often includes psychiatric symptoms such as delusions and hallucinations.
Primary Progressive Aphasia (PPA): This type of FTD may begin to appear in people as young as 40. "Aphasia" is a general term used to refer to deficits in language functions, such as speaking, understanding what others are saying, and naming common objects. In PPA one or more of these functions can become impaired. Symptoms often begin gradually and progress slowly over a period of years. As the disease progresses, memory and attention may also be impaired and patients may show personality and behavior changes. Many, but not all, people with PPA eventually develop symptoms of dementia.
Mixed dementia: This is a condition in which AD and vascular dementia occur at the same time. Recent studies suggest that mixed dementia is more common than previously thought. Brain changes are characterized by the hallmark abnormalities of AD as well as other types—most commonly vascular and LBD. Some experts recommend suspecting this type whenever a person has both evidence of cardiovascular disease and dementia symptoms that worsen slowly.
Rare Forms of Dementia
Rare types of dementia may start with specific primary diseases that cause impairment in different areas and present with very different symptoms. Although these less common types of dementia impact a lesser number of people, their resulting care needs are often quite similar to the more common types of dementia.
HIV-associated Dementia (HAD)
This type results from infection with the human immunodeficiency virus (HIV) that causes AIDS. HAD can cause widespread destruction of the brain's white matter. This leads to a kind of dementia that generally includes impaired memory, apathy, social withdrawal and difficulty concentrating. People with HAD often develop movement problems as well. There is no specific treatment for HAD, but AIDS drugs can delay the onset and may help to reduce symptoms.
Huntington's Disease (HD)
This is a hereditary disorder caused by a faulty gene for a protein called huntingtin. Children of people with the disorder have a 50 percent chance of inheriting it. The disease causes degeneration in many regions of the brain and spinal cord. Symptoms of HD usually begin when patients are in their 30s or 40s, and the average life expectancy after diagnosis is about 15 years.
Cognitive symptoms of HD typically begin with mild personality changes, such as irritability, anxiety, and depression, and progress to severe dementia. Many patients also show psychotic behavior. HD causes chorea—involuntary jerky, arrhythmic movements of the body—as well as muscle weakness, clumsiness, and gait disturbances.
Dementia Pugilistica
Also called chronic traumatic encephalopathy or Boxer's syndrome, this type is caused by head trauma, such as that experienced by people who have been punched many times in the head during boxing. The most common symptoms of the condition are dementia and parkinsonism, which can appear many years after the actually trauma ends. Affected individuals may also develop poor coordination and slurred speech. A single traumatic brain injury may also lead to a disorder called post-traumatic dementia (PTD). PTD is much like dementia pugilistica but usually also includes long-term memory problems. Other symptoms vary depending on which part of the brain was damaged by the injury.
Corticobasal Degeneration (CBD)
This is a progressive disorder characterized by nerve cell loss and atrophy of multiple areas of the brain. CBD usually progresses gradually over the course of 6 to 8 years. Initial symptoms, which typically begin at or around age 60, may first appear on only one side of the body but eventually will affect both sides. Some of the symptoms, such as poor coordination and rigidity, are similar to those found in Parkinson's disease.
Other symptoms may include memory loss, visual-spatial problems, apraxia (loss of the ability to make familiar, purposeful movements), hesitant and halting speech, myoclonus (involuntary muscular jerks), and dysphagia (difficulty swallowing). Death is often caused by pneumonia or other secondary problems such as sepsis (severe infection of the blood) or pulmonary embolism (a blood clot in the lungs).
Creutzfeldt-Jakob Disease (CJD)
This rare, degenerative, fatal brain disorder affects about one in every million people per year worldwide. Symptoms usually begin after age 60 and most patients die within one year. Many researchers believe CJD results from an abnormal form of a protein called a prion. Elderly parents with CJD may initially experience problems with muscular coordination, personality changes, including impaired memory, judgment, and thinking, and impaired vision. Other symptoms may include insomnia and depression. As the illness progresses, mental impairment becomes severe. Patients often develop myoclonus and they may go blind. They eventually lose the ability to move and speak, and lapse into a coma. Pneumonia and other infections often occur in these patients and eventually lead to death.
Diagnosing Dementia
There is no one test to determine if someone has dementia. Doctors diagnose AD and other types based on a careful medical history, a physical examination, cognitive testing, laboratory tests, and the characteristic changes in thinking, day-to-day function and behavior associated with each type. Doctors can make a diagnosis with a high level of certainty, but it is harder to determine the exact type because the symptoms and brain changes of different kinds often overlap. In some cases, a doctor may simply diagnose "dementia" and not specify a type.