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.
Who Is Affected by LBD?
LBD affects an estimated 1.4 million individuals in the United States and accounts for up to 20 percent of people with dementia worldwide. LBD typically begins at age 50 or older, although sometimes younger people have it. LBD appears to affect slightly more men than women.
LBD is a progressive disease, meaning symptoms start slowly and worsen over time. The disease lasts an average of 5 to 7 years from the time of diagnosis to death, but the time span can range from 2 to 20 years. How quickly symptoms develop and change varies greatly from person to person, depending on overall health, age, and severity of symptoms.
In the early stage of LBD, usually before a diagnosis is made, symptoms can be mild, and people can function fairly normally. As the disease advances, people with LBD require more and more help due to a decline in thinking and movement abilities. In the late stage of the disease, they may depend entirely on others for assistance and care.
Some LBD symptoms may respond to treatment for a period of time. Currently, there is no cure for the disease. Research is improving our understanding of this challenging condition, and advances in science may one day lead to better diagnosis, improved care, and new treatments.
The terms used to describe Lewy body dementia (LBD) can be confusing. Doctors and researchers may use different terms to describe the same condition. In this booklet, the term Lewy body dementia is used to describe all dementias whose primary cause is abnormal deposits of Lewy bodies in the brain.
The two types of LBD are:
- dementia with Lewy bodies, in which cognitive (thinking) symptoms appear within a year of movement problems
- Parkinson’s disease dementia, in which cognitive symptoms develop more than a year after the onset of movement problems As LBD progresses, symptoms of both types of LBD are very similar.
What Are Lewy Bodies?
Lewy bodies are named for Dr. Friederich Lewy, a German neurologist. In 1912, he discovered abnormal protein deposits that disrupt the brain’s normal functioning in people with Parkinson’s disease. These abnormal deposits are now called “Lewy bodies.”
Lewy bodies are made of a protein called alpha-synuclein. In the healthy brain, a protein associated with alpha-synuclein plays a number of important roles in neurons (nerve cells) in the brain, especially at synapses, where brain cells communicate with each other. In LBD, alpha-synuclein forms into clumps inside neurons throughout the brain. This process may cause neurons to work less effectively and, eventually, to die. The activities of brain chemicals important to brain function are also affected. The result is widespread damage to certain parts of the brain and a decline in abilities affected by those brain regions. Lewy bodies affect a few different brain regions in LBD:
- the cerebral cortex, which controls many functions, including information processing, perception, thought, and language
- the limbic cortex, which plays a major role in emotions and behavior
- the hippocampus, which is essential to forming new memories
- the midbrain, including the substantia nigra, which is involved in movement
- areas of the brain stem important in regulating sleep and maintaining alertness
- brain regions important in recognizing smells (olfactory pathways)