A progressive neurological condition
Lewy body dementia is a common cause of dementia. It affects attention, movement, sleep and perception, as well as changes in thinking and memory. It is linked to changes in the brain and a build-up of the protein alpha-synuclein.
What is Lewy body dementia?
Lewy body dementia is one of the more common causes of dementia. It affects how alert and focused a person feels, and this can change noticeably, sometimes from hour to hour. A person may seem clear and engaged one moment, then confused or drowsy the next.
Many people may also experience detailed visual hallucinations, often of people or animals. These can feel very real, but they don’t always cause distress or fear.
Movement can also be affected, with slowness, stiffness or a shuffling walk, similar to Parkinson’s disease. Sleep is often disrupted, and some individuals physically act out their dreams, sometimes talking, shouting or moving while asleep (this is called REM sleep behaviour disorder).
Over time, Lewy body dementia can affect:
- attention and alertness (which can change hour to hour)
- independence with everyday tasks
- memory and thinking
- movement (slowness, stiffness or shuffling)
- sleep (acting out dreams, restless nights)
- vision and perception (including hallucinations).
What happens in the brain?
Lewy body dementia happens when clumps of a protein called alpha-synuclein build up inside brain cells. These clumps are called ‘Lewy bodies’, and they affect the parts of the brain that control thinking, movement and sleep.
Over time, this build-up disrupts how the brain works, leading to the symptoms of Lewy body dementia.
What increases the risk of Lewy body dementia?
As with other forms of dementia, no single cause fully explains why Lewy body dementia develops, though several factors are associated with higher risk.
Factors that can’t be changed include:
- age – risk increases with age, and Lewy body dementia most commonly develops in people over 60
- family history – having a close relative with Lewy body dementia or Parkinson’s disease may slightly increase risk, though most cases occur without a clear family history
- REM sleep behaviour disorder – long-standing dream-enactment behaviour is a strong early marker, and many people with this sleep disorder go on to develop Lewy body dementia or Parkinson’s disease
- sex – it appears to be somewhat more common in men than women.
What risk factors may be modifiable?
Factors that may be modifiable (potentially influenced through lifestyle or medical care), are less well established for Lewy body dementia specifically than for Alzheimer’s disease or vascular dementia, but may include:
- cardiovascular health – general vascular risk factors, such as high blood pressure and diabetes, may contribute to overall brain health and could influence symptom severity, though their direct role in causing Lewy body dementia is less clear than in vascular dementia
- physical activity and mental engagement – regular exercise and cognitive engagement are generally associated with better brain health, though specific evidence for reducing Lewy body dementia risk is more limited than for other dementia types.
Common patient questions
Not exactly. They involve the same protein change (alpha-synuclein) in the brain, but doctors tell them apart based on which symptoms come first:
- in Lewy body dementia, thinking changes appear before, or within a year of, movement symptoms
- in Parkinson’s disease dementia, movement symptoms come first, and thinking changes tend to develop at least a year later.
Early signs commonly involve fluctuating attention, visual hallucinations, or a movement change such as slowness or stiffness, rather than memory loss alone.
Visual hallucinations happen because the disease affects the parts of the brain that process what we see. They’re often detailed, such as seeing people or animals, and don’t always feel frightening.
Some medicines, particularly certain ones used to treat agitation or hallucinations, can cause serious side effects in people with Lewy body dementia. It is important that every doctor involved in the patient’s care knows about the diagnosis before prescribing anything new.