Lewy body dementia (LBD) is one of the most common types of dementia, after Alzheimer’s disease. It usually affects people aged 50 or older. Lewy bodies are clumps of protein that can form in the brain. When they build up, they can cause problems with the way your brain works, including your memory, movement, thinking skills, mood, and behavior. There are two types of LBD: Dementia with Lewy bodies often starts when you have a hard time moving your body.