�ٺ���Ƶ

Dementia is a term used to describe symptoms such as memory loss or a decline in a person’s thinking and reasoning skills that interferes with daily life. Such symptoms might also be seen in mild cognitive impairment, a condition that may or may not progress to dementia, but the symptoms don’t interfere with a person’s ability to live independently.

In dementia, symptoms occur when nerve cells in the brain die. Brain cell death happens to everyone with age, but dementia is not a normal part of aging. Rather, people with dementia often become increasingly forgetful, disoriented, or unable to control their emotions. They may exercise poor judgment or experience agitation, delusions, and hallucinations. 

There are many types of dementia. Symptoms may result from a condition such as Alzheimer’s disease or a stroke and develop over a long period of time. Some people have a combination of more than one type of dementia, called mixed-type dementia. Most types affect people over the age of 65, but people in their 40s or 50s can also develop symptoms of dementia. When a person under age 65 is diagnosed with dementia, it is called early-onset dementia. 

Many other health conditions can cause dementia-like symptoms. Some of these, such as depression, hypothyroidism, and vitamin deficiencies, may be reversible, meaning that dementia symptoms lessen or even disappear with treatment.

�ٺ���Ƶ doctors can distinguish the types of dementia in order to recommend the most appropriate treatment.

Alzheimer’s Disease

Alzheimer’s disease, the most common form of dementia in older people, is a progressive type, meaning the condition worsens over time. It isn’t a normal part of the aging process, though risk increases after age 65; about one-third of all people over the age of 85 have the disease. 

People with Alzheimer’s disease have worsening memory loss and trouble with language that interferes with their daily lives. With time, they become increasingly confused and disoriented, find it difficult to make decisions, and show changes in their behavior and personality. Eventually, a person with the condition becomes less able to care for himself or herself.

Vascular Dementia

In this type of dementia, the second most common type after Alzheimer’s disease, a blood vessel injury or disease reduces blood flow to certain parts of the brain. When brain cells don’t get enough oxygen-rich blood, they die, weakening thinking skills. 

This can happen after a major stroke, but many small strokes or other conditions that affect blood vessels in the brain can cause more gradual thinking changes, as damage to the blood vessels accumulates. Symptoms of vascular dementia include memory loss, trouble speaking or understanding speech, confusion and disorientation, and vision loss. The degree of memory loss depends on which areas of the brain are affected by reduced blood flow. 

Conditions associated with vascular dementia may include hypertension, diabetes, and high cholesterol. This is also a progressive form of dementia, though the rate at which it progresses varies. 

Lewy Body Dementia

Lewy body dementia encompasses two conditions—Parkinson’s disease dementia and dementia with Lewy bodies—that together constitute the third most common type of dementia after Alzheimer’s disease and vascular dementia. Lewy body dementia involves confusion and hallucinations, along with the movement problems seen in Parkinson’s disease, such as tremor and rigidity. 

People whose dementia symptoms occur before or within one year of Parkinson’s symptoms receive a diagnosis of dementia with Lewy bodies. People who have an existing diagnosis of Parkinson’s disease for more than a year and later develop symptoms of dementia receive a diagnosis of Parkinson’s disease dementia.

In this type of dementia, abnormal clumps of proteins, called Lewy bodies, develop in areas of the brain that control aspects of thinking and movement. Researchers don’t know exactly why Lewy bodies form or how they cause symptoms. People with Lewy body dementia often have fluctuations in alertness and attention; recurrent hallucinations; problems with sleep; and Parkinson-like symptoms such as a shuffling walk. Memory loss may not develop at first but becomes more apparent as time goes on. 

This type of dementia generally affects people older than age 50.

Frontotemporal Dementia

This condition affects the brain’s frontal lobes—the area behind the forehead—and the temporal lobes—the area close to the ears. These two lobes govern personality, behavior, language, and reasoning. In frontotemporal dementia, portions of these lobes atrophy, or shrink, causing symptoms that can include dramatic changes in how a person behaves and speaks. Over time, frontotemporal dementia makes it difficult for people to plan, interact socially, and take care of themselves. 

This type of dementia affects people between the ages of 40 and 65 and accounts for roughly 10 percent of all dementias.