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There are two types of dementia closely related to Parkinson's disease: dementia with Lewy bodies and Parkinson's dementia.

3D illustration of Lewy body accumulation in Parkinson's disease
A 3D illustration showing Lewy body accumulation in brain cells in Parkinson's disease

Parkinson's dementia and dementia with Lewy bodies are often referred to under the umbrella term Lewy body dementias (LBD), as both involve the accumulation of a protein called alpha-synuclein into clumps known as Lewy bodies within brain cells. The two types also share some of the same symptoms, like sleep disturbances, thinking and memory problems, and movement difficulties.

The key difference is when different symptoms first appear. In dementia with Lewy bodies, the symptoms of dementia present within a year of the movement symptoms. In Parkinson's dementia, the movements typical of Parkinson's disease will have already been present for at least a year when the dementia symptoms appear.

In dementia with Lewy bodies, people often first experience symptoms that are very similar to Alzheimer's disease, such as confusion or issues with decision-making and planning. However, as the disease progresses, other symptoms develop that distinguish it from other types of dementia, which may include:

  • Visual hallucinations that develop earlier than they would do in Alzheimer's disease
  • A sleep disorder during the dreaming phase of sleep (REM sleep behaviour disorder) that involves the person acting out their dreams
  • Cognitive (thinking) issues that relate more to problem solving, attention and multi-tasking than to the memory issues more commonly associated with dementia
  • Movement difficulties known as Parkinsonian symptoms

In Parkinson's disease, the first area affected by Lewy bodies is the part of the brain that controls movement. This means the early symptoms are tremors, shaking, rigid muscles, shuffling, stooping, and trouble initiating movement. As the condition progresses, the damage spreads to other brain regions. This results in symptoms of dementia, which can include memory, planning, attention and thinking problems, as well as disturbances in mental health. At this stage, a diagnosis of Parkinson's dementia is given.

Eighty-three per cent of people who have been diagnosed with Parkinson's disease for at least 20 years also have dementia. If people are diagnosed with Parkinson's disease when they are older, have mild cognitive impairment, or more severe movement issues, they may have an increased risk of dementia.

Unfortunately, because of the overlap between Parkinson's and Alzheimer's disease, LBD is often misdiagnosed. This can mean people not getting the tailored support they require to live well. However, the Lewy Body Society is working hard to change that, as well as providing help and support for people diagnosed with LBD.

As well as the standard medication for Parkinson's disease – which is called L-Dopa – there are many ways to help manage the symptoms of LBD. Occupational therapists, whose job it is to ensure people's physical environment is as safe as possible, can be especially helpful for people with LBD because of the movement difficulties. For the same reason, physiotherapists can help ensure no physical issues are exacerbating the person's movement.

Medicines designed to treat Alzheimer's disease can also help people with LBD, as they help boost the chemical messengers in the brain, enabling people to think more clearly. If the person's hallucinations are becoming distressing, there are also medicines available to treat that. Plus, sleep medication can be helpful against the sleep issues associated with dementia with Lewy bodies.

Ultimately, it's important for people with LBD to discuss their individual symptoms with their doctor to ensure they get the right treatment for them. As with all types of dementia, group activities such as memory cafes and other social groups can improve an individual's mood and thinking skills. Plus, physical activities like walking and tai chi can help to slow the deterioration of motor skills – there's even a ballet group especially tailored for people with Parkinson's disease.

Like every type of dementia, it is possible to live well with Parkinson's dementia and dementia with Lewy bodies. There are lots of charities that can help make this happen, including Rare Dementia Support, Parkinson's UK, and Alzheimer's Society.

Parkinson's Awareness Week 2021 takes place from 6-11 April in the UK.