What is Dementia?
Dementia is a term used to describe the loss of memory and cognitive abilities severe enough to alter a person’s daily activities and independence. Dementia is not one disease; it is an umbrella term for many diseases that have memory loss as a symptom. It is caused by abnormal, altered brain function due to damage and death of brain cells. It is typically progressive, with increasing impairment over time. Although dementia is generally seen in the older population, it is not a part of normal healthy aging and, having memory loss alone, does not mean that you have dementia.
Dementia Statistics
Worldwide around 50 million people are living with dementia and this number is projected to increase to 152 million by 2050 (data from: https://apo.org.au/node/260056). This number is especially rising in low-income and middle-income countries where around two-thirds of people with dementia live (data from: https://apo.org.au/node/260056). Dementia has a global cost of about $1 trillion annually.
More than 432,000 seniors aged 65 and older are living with dementia in Canada and this number continues to rise each year. About 1 in 4 seniors age 85 and older have been diagnosed with dementia and about two-thirds of Canadian seniors living with dementia are women. Annually, there are approximately 76,000 new cases of dementia diagnosed. (Data from: https://www.canada.ca/en/public-health/services/publications/diseases-conditions/dementia-highlights-canadian-chronic-disease-surveillance.html). Of Canadians living in long-term care with dementia, 31% have depression. The overall risk of dying from any cause was 4.4 times higher among Canadians 65 years of age and older living with dementia compared to those without. (Data from: https://health-infobase.canada.ca/datalab/dementia-alzheimers-blog.html).
Types of Dementia
Alzheimer’s disease
Alzheimer’s disease is the most common neurodegenerative disease responsible for dementia. Pure Alzheimer’s disease accounts for about 27% of dementias, but when considering Alzheimer’s disease with other vascular complications it accounts for 60-80% of cases. The most common form occurs sporadically, due to a combination of factors such as a person’s genes, their environment and lifestyle; this form of the disease progresses slowly. The second is a rare familial form that occurs because of the genes that a person has inherited from their parents. Familial Alzheimer’s disease is typically diagnosed before the age of 65 and is quicker to progress than sporadic Alzheimer’s disease.
Alzheimer’s disease is defined by two types of brain deposits called plaques and tangles. Plaques are deposits of a protein called beta-amyloid in the blood vessels of the brain and in the brain itself. They become toxic to cells at increased levels. Tangles are deposits of a protein called tau which interferes with the cells in the brain and eventually causes them to die. Overall, the brain begins to shrink from the loss of cells resulting in a reduction of cognitive ability.
Early signs of Alzheimer’s disease are difficulties in remembering things such as names and recent events. Depression may also accompany the memory loss.
Vascular dementia
Vascular dementia is the second most common form of dementia and is estimated to make up approximately 10-15% of all dementias. It occurs when the blood vessels in the brain become damaged or narrowed causing reduced blood circulation. Narrowing can happen because of build up of fats and cholesterol (atherosclerosis) which reduces the amount of oxygen and nutrients delivered to the brain and overtime cells can die. Vascular dementia can also occur following a stroke, a brain hemorrhage, or other conditions that affect the blood supply. Detecting this type of dementia early and controlling the risk factors can help to reduce the severity of symptoms. This means controlling high blood pressure, diabetes, and high cholesterol and not smoking.
The symptoms of vascular dementia can vary depending on the part of the brain where the blood flow is impaired. Early signs can include problems with short-term memory, difficulties with planning, problem-solving, and slowed thinking, focus and organization.
Lewy body dementia
Lewy body dementia is estimated to be the third most common cause of dementia, accounting for 5-10% of dementias. This type of dementia occurs because abnormal deposits of protein called Lewy bodies build up in the brain and cause damage to cells over time. Lewy bodies are made up of a protein called alpha-synuclein. This protein is important for neurons but when it builds up beyond normal levels in the brain, it causes the cells to become damaged and eventually die.
Early symptoms can be mild but as the disease progresses the symptoms can be similar to Alzheimer’s disease; however, the loss of memory may not occur early on. Instead, it is declines in thinking and reasoning that occur first in this type of dementia. Visual hallucinations may also be common, along with muscle stiffness, tremors and shuffling movements.
Lewy bodies are also found in other brain disorders, including Alzheimer’s disease, Parkinson’s disease dementia and schizophrenia.
Parkinson’s disease dementia
Although Parkinson’s disease is commonly thought of as a movement disorder, many people who have Parkinson’s disease will also develop dementia. Parkinson’s dementia is diagnosed if the onset of dementia occurs a year or more after the onset of motor symptoms. If the symptoms of dementia occur at the same time as the motor symptoms, it is diagnosed as Lewy body dementia. Typically Lewy bodies are found in patients with Parkinson’s dementia, which contribute to the onset of dementia. How long the person has had Parkinson’s disease and the stage that they are at, determines the likelihood of having dementia. Approximately 30% of people with Parkinson’s disease do not develop dementia.
Early signs are impairments with problem solving, speed of thinking, memory and changes in mood.
Frontotemporal dementia
This encompasses several types of dementia that all affect the front and sides of the brain. This disease results in the degeneration of the cells and connections in the parts of the brain that are responsible for personality, behaviour, and language. These disorders are among the most common of the dementias that begin at a younger age, typically between 40-65 years of age. Although the cause is unknown, several gene variants have been linked to subtypes of frontotemporal dementia. In addition, in some cases, small structures called Pick bodies have been found in the brains of people with this type of dementia. These Pick bodies contain an abnormal amount or type of protein.
Symptoms start gradually and progress steadily. Memory is not initially affected and early signs are loss of one’s inhibitions and an increase in compulsive behaviours. Thinking and judgement are also affected. Eventually, people may have problems with speech and forget the meaning of common words.
Creutzfeldt-Jakob disease
Creutzfeldt-Jakob disease is one of the rarest forms of dementia with 1 in one million people being diagnosed per year. The cause of this type of dementia is the abnormal production of a type of protein called prion proteins. These proteins are normally produced in the body and are harmless, however, when they are misshapen they become infectious and can interfere with normal biological processes. Most people that are diagnosed have developed this disease for no apparent reason, it has happened sporadically. Fewer than 15% of people with CJD have a family history of the disease or test positive for a genetic mutation known to cause the disease.
CJD progresses very quickly and people tend to die within one year of diagnosis. Early signs are agitation, depression, confusion and loss of memory. It can also affect the muscles, causing twitching and stiffness.
Wernicke-Korsakoff syndrome
This syndrome is actually two separate conditions that can occur at the same time. Wernicke’s disease is caused by a lack of vitamin B-1 which is vital for brain cells to work properly. This results in swelling of the brain, called encephalopathy, causing double vision, confusion and lack of motor coordination. If this condition is not treated quickly, it will progress to Korsakoff syndrome and the brain will become permanently damaged producing symptoms similar to that of dementia.
Alcoholism or chronic alcohol misuse is the most common cause of Wernicke syndrome, but it is also linked to diet deficiencies or other medical conditions that can impair the absorption of vitamin B-1.
Mixed dementia
It is very common for those with dementia to have mixed dementia where two or more types of dementia are present. Clinicians are recognizing that mixed dementia may in fact be the most common type of dementia. It is most common to have a combination of Alzheimer’s disease, with plaques and tangles present in the brain, with vascular dementia and/or Lewy bodies, however a number of combinations are possible. Mixed dementia symptoms are variable, depending on the brain changes and areas affected. Symptoms may be similar to Alzheimer’s disease or another type of dementia. However, in other cases, symptoms may be indicative of the existence of more than one type of dementia.
Normal pressure hydrocephalus
Normal pressure hydrocephalus is due to a build up of fluid, called cerebrospinal fluid, in the fluid cavities of the brain. This fluid bathes the brain and spinal cord, cushioning them during movements. When the fluid does not drain properly it creates pressure that can cause damage leading to dementia symptoms. Approximately 5% of dementia cases are due to normal pressure hydrocephalus. The reason for this fluid build up could include injury, bleeding, infection, or brain tumor.
Early signs include poor balance, forgetfulness, and loss of bowel or bladder control. The good news is that once the underlying cause is determined, the fluid build up can be drained, either through the placement of a shunt or through a procedure called a lumbar puncture.
Huntington’s disease
Huntington’s disease is an inherited condition which causes the degeneration of the neurons in an area of the brain that is responsible for movement and coordination. It is a progressive disease which results in involuntary movements, behavioural and personality changes and cognitive decline. The gene mutation that causes Huntington’s disease can be passed down generationally. As there is variability in the expression of Huntington’s disease it can be categorized into a rare juvenile onset or more common adult onset.
Early signs are personality changes, impaired movements, difficulty walking, trouble swallowing and trouble speaking, along with difficulty focusing on tasks. People with Huntington’s disease may also initially have symptoms of memory and learning difficulties, as well as impaired judgement and impulse control.
Posterior cortical atrophy
Posterior cortical atrophy is a rare neurodegenerative disease that results in a slow progressive decline in vision. The atrophy in this brain region, located at the back of the brain, may be due to other types of dementia such as Alzheimer’s disease, Lewy body dementia or other neurological conditions. It tends to affect people at an earlier age than typical Alzheimer’s disease, with individuals usually being in their mid-fifties or early sixties when they first experience symptoms.
Early symptoms include blurred vision, difficulties with reading, judging distances and recognizing objects or familiar faces. Over time it can lead to memory and cognitive decline.
Other causes of dementia
Many diseases can have a symptom of dementia, especially in the later stages. Those with Multiple Sclerosis or HIV can develop cognitive impairment.