Quick GuideDementia, Alzheimer's Disease, and Aging Brains

Lewy body dementia includes two related conditions - dementia with Lewy bodies and Parkinson’s disease dementia. The difference between them lies largely in the timing of cognitive (thinking) and movement symptoms. In dementia with Lewy bodies, cognitive symptoms are noted within a year of parkinsonism, any condition that involves the types of movement changes seen in Parkinson's disease. In Parkinson's disease dementia, movement symptoms are most pronounced, with cognitive symptoms developing years later.

People with dementia with Lewy bodies first have a decline in cognitive skills that may look somewhat like Alzheimer’s disease. But over time they also develop movement and other distinctive symptoms that suggest dementia with Lewy bodies.

Symptoms that distinguish this form of dementia from others may include:

• visual hallucinations early in the course of dementia
• fluctuation in cognitive ability, attention, and alertness
• slowness of movement, difficulty walking, or rigidity (parkinsonism)
• sensitivity to medications used to treat hallucinations
• REM sleep behavior disorder, in which people physically act out their dreams
• more trouble with complex mental activities, such as multitasking, problem solving, and analytical thinking, than with memory

This type of LBD starts as a movement disorder, with symptoms such as slowed movement, muscle stiffness, tremor, or a shuffling walk. These symptoms lead to a diagnosis of Parkinson's disease. Later on, cognitive symptoms of dementia and changes in mood and behavior may arise.

Not all people with Parkinson's develop dementia, and it is difficult to predict who will. Being diagnosed with Parkinson's late in life is a risk factor for Parkinson's disease dementia.

LBD is a disease associated with abnormal deposits of a protein called alpha-synuclein in the brain. These deposits, called Lewy bodies, affect chemicals in the brain whose changes, in turn, can lead to problems with thinking, movement, behavior, and mood. LBD is one of the most common causes of dementia, after Alzheimer’s disease and vascular disease.

Dementia is a severe loss of thinking abilities that interferes with a person's capacity to perform daily activities such as household tasks, personal care, and handling finances. Dementia has many possible causes, including stroke, tumor, depression, and vitamin deficiency, as well as disorders such as LBD, Parkinson's, and Alzheimer's.

Diagnosing LBD can be challenging for a number of reasons. Early LBD symptoms are often confused with similar symptoms found in brain diseases like Alzheimer's. Also, LBD can occur alone or along with Alzheimer's or Parkinson's disease.

There are two types of LBD - dementia with Lewy bodies and Parkinson's disease dementia. The earliest signs of these two diseases differ but reflect the same biological changes in the brain. Over time, people with dementia with Lewy bodies or Parkinson's disease dementia may develop similar symptoms.

The precise cause of LBD is unknown, but scientists are learning more about its biology and genetics. For example, they know that an accumulation of Lewy bodies is associated with a loss of certain neurons in the brain that produce two important neurotransmitters, chemicals that act as messengers between brain cells. One of these messengers, acetylcholine, is important for memory and learning. The other, dopamine, plays an important role in behavior, cognition, movement, motivation, sleep, and mood.

Scientists are also learning about risk factors for LBD. Age is considered the greatest risk factor. Most people who develop the disorder are over age 50.

Other known risk factors for LBD include the following:

• Diseases and health conditions: Certain diseases and health conditions, particularly Parkinson's disease and REM sleep behavior disorder, are linked to a higher risk of LBD.
• Genetics: While having a family member with LBD may increase a person's risk, LBD is not normally considered a genetic disease. A small percentage of families with dementia with Lewy bodies has a genetic association, but in most cases, the cause is unknown. At this time, no genetic test can accurately predict whether someone will develop LBD. Future genetic research may reveal more information about causes and risk.
• Lifestyle: No specific lifestyle factor has been proven to increase one's risk for LBD. However, some studies suggest that a healthy lifestyle - including regular exercise, mental stimulation, and a healthy diet - might reduce the chance of developing age-associated dementias.