INTRODUCTION
It's estimated that about 50% of people age 85 and older have dementia. Current medications
may help slow the mental decline. It develops when the parts of your brain involved with
learning, memory, decision- making or language are affected by infections or
diseases.
Epidemiology
About 5% to 8% of all people over the age of 65 have some form of dementia, and this number
doubles every five years above that age. It's estimated that as many as half of people 85
years of age and older have dementia.
Classification
Dementias can be divided into three Groups:
• Primary (diseases and conditions in which dementia is the main illness).
• Secondary (dementia due to another disease or condition).
• Reversible dementia-like symptoms caused by other illnesses or causes.
Primary dementia
• Alzheimer's disease: This is the most
common type of dementia. Two abnormal proteins build up in your brain: tau and amyloid
proteins. These proteins disrupt communication between nerve cells in your
brain. Nerve cells die, starting in one area and spreading as more nerve cells die in other
areas.
Vascular dementia: This is the second most common type of dementia. It's caused by
conditions such as strokes or atherosclerosis, which block and damage blood vessels in your brain. The decline may appear suddenly (following a major stroke) or in steps (following a series of mini-strokes). Risk
factors include high blood pressure, diabetes, and high cholesterol levels. About 15%, to 25%,
of people with dementia have vascular dementia.
• Frontotemporal dementia (FTD): This dementia results from damage to the frontal and temporal lobes of your brain. The damage is caused by the buildup of abnormal proteins in these areas. It causes changes in social behavior, personality, and loss of language skills (speaking, understanding, or forgetting the meaning of common words) or motor coordination. FTD İs a common cause of early dementia, often occurring in people between the ages of 45 and 64. Between 5%, and 6%, of
all dementias are FTD.
• Mixed dementia: This is a combination of two or more types of dementia. The most common combination is Alzheimer's disease with vascular dementia. It's most common in people 80 years of age and over. It's often hard to diagnose because symptoms of one dementia may be more obvious and/or many symptoms of each type overlap. The decline is
faster in people who have mixed dementia compared with those who only have one type.

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