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, such as tremor or muscle stiffness, seen in Parkinson’s disease. In Parkinson’s disease dementia, movement symptoms are pronounced in the early stages, with cognitive symptoms developing years later.
Dementia with Lewy Bodies
People with dementia with Lewy bodies have a decline in thinking ability 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
fluctuations 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 by yelling, flailing, punching bed partners, and falling out of bed
more trouble with complex mental activities, such as multitasking, problem solving, and analytical thinking, than with memory
Parkinson’s Disease Dementia
This type of LBD starts as a movement disorder, with symptoms such as slowed movement, muscle stiffness, tremor, and a shuffling walk. These symptoms are consistent with 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.