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Causes of dementia
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Dementia is usually caused by degeneration in the cerebral cortex, the part of the brain responsible for thoughts, memories, actions and personality. Death of brain cells in this region leads to the cognitive impairments that characterise dementia.
Some causes of dementia are treatable. These include, among others: head injury, brain tumours, infections (such as meningitis, HIV / AIDS, or syphilis), simple and normal pressure hydrocephalus (when the fluid in which the brain floats is collecting outside or in the cavities of the brain, compressing it from outside), hormone disorders (that is, disorders of hormone-secreting and hormone-regulating organs such as the thyroid gland), metabolic disorders (such as diseases of the liver, pancreas, or kidneys that disrupt the balances of chemicals in the blood), hypoxia (poor oxygenation of the blood), nutritional (vitamin) deficiencies, drug abuse, or chronic alcoholism.
Unfortunately, most disorders associated with dementia are progressive (inducing a gradual decline of functioning), degenerative (getting steadily worse over time), and irreversible. The two major degenerative causes of dementia are Alzheimer's Disease (the progressive loss of nerve cells without known cause) and vascular dementia (loss of brain function due to a series of small strokes).
Alzheimer’s Disease is the most common irreversible cause of dementia, accounting for 50% to 70% of all dementia cases. In this disease, abnormal deposits of protein in the brain destroy cells in the areas of the brain that control memory and mental functions. People with Alzheimer disease also have lower-than-normal levels of brain chemicals called neurotransmitters that control important brain functions. The brain of a person with Alzheimer disease is also clogged with two abnormal structures (called neurofibrillary tangles and senile plaques). However, why these structures develop is still unknown.
There are two known risk factors for developing Alzheimer's Disease.
- Advancing age is the number one risk factor. About 5 % of people above 65 years of age, about 20 % of those over 80 years and about 30 % of those over 90 suffer from Alzheimer's disease.
- Family history is the second risk factor. People who have a parent or sibling affected by Alzheimer's are two to three times more likely to develop the disease than those with no family history. If more than one close relative has been affected by the disease, the risk increases even more. In rare case, the disease is completely inherited (Familial Alzheimer’s Disease occurs in less than 1% of all Alzheimer’s Disease cases).
Vascular dementia is the second most common cause of dementia, accounting for about 20% of cases. This dementia is caused by atherosclerosis, caused by, for example, deposits of fats, dead cells, and other debris that form on the inside of arteries and partially (or completely) block blood flow. These blockages may cause multiple strokes, or interruptions of blood flow, to the brain. Because this interruption of blood flow is also called “infarction,” this type of dementia is sometimes called multi-infarct dementia. Vascular dementia is often related to high blood pressure, high cholesterol, heart disease, diabetes, and related conditions. Treating those conditions can slowdown the progress of vascular dementia, but functions do not come back once they are lost.
Vascular Dementia may occur at the same time as Alzheimer's Disease, resulting in a condition called Mixed Dementia.
Other irreversible medical conditions that can also cause dementia (at a much lower rate) include, for example, Parkinson’s disease, Huntington’s Disease, Pick’s Disease, or Creutzfeldt-Jakob Disease.
