The many forms of dementia
Last Updated October 16, 2007
Canada's population — like the populations of most developed nations — is getting a lot older. And the change is happening quickly.
In 1981, about 10 per cent of Canadians were aged 65 or older. By 2026, that figure will be closer to 25 per cent, according to projections by Statistics Canada.
As a result, the number of people affected by dementia — a collection of symptoms that significantly impair thinking, and normal activities and relationships — is increasing substantially. About eight per cent of people over 65 have some form of dementia.
The older you get, the higher your risk of developing dementia.
Dementia is characterized by confusion, disorientation and intellectual impairment. It's estimated that one in five people with dementia will become aggressive and can pose a danger to himself or herself, caregivers, or the people he or she lives with, either at home or in a residential facility.
There are several forms of dementia. They include:
Alzheimer's disease is the most common cause of dementia in people 65 and older. Nearly all brain functions, including memory, movement, language, judgment, behaviour, and abstract thinking, are eventually affected. An estimated 290,000 Canadians — or about one in 20 — have Alzheimer's. The number rises to one in four over age 85.
Binswanger's disease — also called subcortical vascular dementia — is a rare form of dementia characterized by damage to small blood vessels in the white matter of the brain. The damage, the result of hardening of the arteries to the brain, leads to brain lesions, loss of memory, disordered cognition and mood changes. It is a progressive disease and there is no cure.
Cortical dementias are characterized by damage to the brain's cortex, or outer layer. These patients can show severe memory impairment and aphasia, the inability to recall words and understand everyday language. Alzheimer's and Creutzfeldt-Jakob disease are both cortical dementias. Both are progressive diseases and will eventually kill.
Creutzfeldt-Jakob disease — also called the human form of so-called mad cow disease — is a rare, degenerative, fatal brain disorder that is believed to be linked to an abnormal form of a protein called a prion. CJD kills an average of one person in a million every year. Most are elderly. CJD has been shown to be transmitted through contact with infected people's brains, via insufficiently sterilized surgical instruments and electrodes applied directly into the brain, and through growth hormone created from infected corpses. People who eat meat contaminated by mad cow disease also may be at risk of contracting a form of CJD.
Dementia pugilistica is a form of dementia caused by head trauma such as that experienced by boxers. It is also called chronic traumatic encephalopathy, or Boxer's syndrome. Jack Dempsey, Joe Louis, Floyd Patterson, Jerry and Mike Quarry, and Muhammad Ali are all believed to have suffered from the ailment. In boxers, symptoms tend to show up 12 to 16 years after the beginning of a career.
Frontotemporal dementias are characterized by degeneration of nerve cells, especially those in the frontal and temporal lobes of the brain. Originally called Pick's disease, people suffering from these dementias exhibit symptoms similar to Alzheimer's disease. There is no known treatment to slow the progression of frontotemporal dementias. The disease progresses fairly rapidly — from two to 10 years. Patients will eventually require 24-hour care.
HIV-associated dementia usually develops several years after a person is infected with the human immunodeficiency virus that causes AIDS and is often seen as the onset of full-blown AIDS. It can cause widespread destruction of the brain's white matter. Symptoms include mental slowness, memory loss, difficulty in concentration, clumsiness, poor balance, tremors, as well as apathy and lethargy.
Huntington's disease is a degenerative hereditary disorder caused by a faulty gene for a protein called huntington. The disease causes degeneration in many regions of the brain and spinal cord, resulting in uncontrolled movements, loss of intellectual faculties and emotional disturbance. A child has a 50-50 chance of developing HD if one parent has it. Early symptoms include mood swings, depression, irritability, and trouble learning new things, making a decision or remembering facts. There is no cure but symptoms can be managed through drug treatment. People diagnosed with the disease normally live another 15 to 20 years and usually die of something else.
Lewy body dementia
Lewy body dementia is the second most common type of progressive dementia, accounting for about 20 per cent of all dementia cases. It is characterized by the presence of abnormal structures called Lewy bodies in the brain. The symptoms are similar to those of Alzheimer's disease, including loss of memory, judgment and reasoning, and changes in mood, behaviour and communication abilities. Lewy body dementia can occur on its own, or with Alzheimer's disease or Parkinson's disease. The cause is unknown and there is no cure.
Multi-infarct dementia — or vascular dementia — is a common cause of memory loss among the elderly. It is a type of vascular dementia caused by several small strokes in the brain. These strokes sometimes occur with no noticeable symptoms and are referred to as "silent strokes." The brain damage cannot be reversed and the patient usually gets worse over time. Sometimes the patient may appear to improve slightly, but often declines again after suffering more silent strokes.
Parkinson's dementia sometimes occurs in people with advanced Parkinson's disease, which is primarily a movement disorder. It's not clear what causes dementia in Parkinson's patients. People with the disorder will experience some of the same symptoms as Alzheimer's patients, as well as their Parkinson's symptoms. Many Parkinson's patients have the characteristic amyloid plaques found in Alzheimer's disease, but it is not clear if the diseases are linked.
Progressive supranuclear palsy
Progressive supranuclear palsy (PSP) is a rare degenerative brain disorder that affects a person's balance and gait. It affects approximately one in 100,000 people over the age of 60. Early symptoms include a loss of balance while walking, changes in personality, irritability and forgetfulness. Unexplained falls or a stiffness and awkwardness in gait are also fairly common.
Patients also tend to suffer from depression, apathy and mild dementia.
There is no cure and no effective treatment. The condition is not fatal, however, patients are susceptible to serious secondary complications including pneumonia, difficulty in swallowing and a tendency to fall. The most common cause of death for PSP patients is pneumonia.
Post-traumatic dementia is brought on by a single traumatic brain injury. It is uncommon and is much like dementia pugilistica, but usually also includes long-term memory problems.
Substance-induced persisting dementia
Substance-induced persisting dementia can occur in people who regularly abuse alcohol and/or recreational drugs. The symptoms can persist even after the substance abuse has ended.
Not all memory loss is dementia
You may show some symptoms and not have dementia. For instance, it is normal for aging people to show some decline in brain function. As we age, our brains may shrink a bit and some nerve cells will die. This can result in mild memory impairment and slower information processing. Age-related cognitive decline is normal and not the onset of dementia.
Some people may develop mild cognitive impairment. Symptoms would be more pronounced than those associated with normal aging, but still not severe enough to be considered dementia. Not all patients with this level of impairment develop dementia, although many eventually will.
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