Dementia with Lewy bodies (DLB) is a type of dementia accompanied by changes in behavior, cognition, and movement. As a progressive illness, it is usually diagnosed when cognitive decline interferes with normal daily functioning. A core feature is REM sleep behavior disorder (RBD), in which people lose normal muscle paralysis during REM sleep and act out their dreams. Memory loss is not always an early symptom, RBD may appear years or decades before other symptoms. Other frequent symptoms include visual hallucinations, marked fluctuations in attention or alertness, and slowness of movement, trouble walking, or rigidity. The autonomic nervous system is usually affected, resulting in changes in blood pressure, heart and gastrointestinal function, with constipation as a common symptom. Mood changes such as depression and apathy are common.
The exact cause is unknown, but involves widespread deposits of abnormal clumps of alpha-synuclein protein known as Lewy bodies in neurons, as well as Lewy neurites. DLB is not usually inherited, but there is a genetic association in a small number of families. A probable diagnosis is made based on symptoms and biomarkers; which may include blood tests, neuropsychological tests, medical imaging, and polysomnography. Other conditions that share some symptoms of DLB include Alzheimer's disease (AD), Parkinson's disease, delirium, and rarely, psychosis.
There is no cure, and no medication can modify its progression. Treatments aim to relieve some of the symptoms and reduce the burden on caregivers. Acetylcholinesterase inhibitors, such as donepezil and rivastigmine, are effective at improving cognition and overall functioning, and melatonin can be used for sleep-related symptoms. Antipsychotics are usually avoided, even for hallucinations, because people with DLB are sensitive to them, and their use can result in death. Medications for one symptom may worsen another.
DLB is one of the three most common types of dementia, along with Alzheimer's, and vascular dementia. Together with Parkinson's disease dementia, it is one of two dementias classified as the Lewy body dementias. It typically begins after the age of 50, and about 0.4% of people over 65 are affected. People in the latter stages of DLB may be unable to care for themselves. Life expectancy following diagnosis is about eight years. The abnormal deposits of protein that are the underlying mechanism of the disease were discovered in 1912 by Frederic Lewy, and diffuse Lewy body disease was first described by Kenji Kosaka in 1976.