Why is Lewy body dementia so hard to spot?

Tiny clumps, two diagnoses

Lewy bodies are tiny clumps of protein that build up inside nerve cells in the brain^{2, 3}. Their main ingredient is a protein called alpha-synuclein^{7, 8}.

"Lewy body dementia" is often used as an umbrella term for two related diagnoses: dementia with Lewy bodies (DLB) and Parkinson's disease dementia^{7, 8}. In DLB, dementia symptoms begin before or around the same time as movement problems; in Parkinson's disease, dementia often develops many years after the movement problems start³.

Symptoms that come and go

One hallmark is fluctuation: confusion and alertness can change from hour to hour, or even within minutes^{4, 10}.

Up to 80% of people with DLB have recurrent visual hallucinations, typically well-formed images of people, children or animals¹⁰.

Movement can become slow and stiff, sometimes with trembling, much like Parkinson's disease; up to two-thirds of people with DLB have movement difficulties when diagnosed⁴.

At night, some people physically act out their dreams, a condition called REM sleep behaviour disorder^{4, 7}. It often begins many years before other symptoms¹⁰.

Why it is so easy to miss

People with DLB are often misdiagnosed, usually with Alzheimer's disease^{5, 10}.

Memory, the symptom most people link with dementia, is often less affected early on than in Alzheimer's^{2, 4, 7}. Because abilities vary from day to day, a test on a 'good day' can miss problems⁵.

Many people with DLB also have the protein build-ups that cause Alzheimer's³; having both kinds of brain change is called mixed dementia⁷.

There is no single test². Scans can help⁵, but the Alzheimer's Association says only a post-mortem examination can diagnose DLB conclusively⁷.

In a 2010 study using data from 31 academic medical centres, diagnoses made in life caught only 32.1% of pure DLB cases and 12.1% of mixed Alzheimer's-and-DLB cases, compared with post-mortem findings¹². The DLB Consortium still called detection rates in clinical practice suboptimal in 2017¹⁰.

How common is it?

The Alzheimer's Society says about 1 in 10 people with dementia has DLB, that only around 5% of people diagnosed with dementia are recorded as having it, and that scientists think it may account for up to 20% of all dementia³. A systematic review found DLB in 4.2% of diagnosed dementia in the community and 7.5% in specialist care, adding that the true figure is likely much higher¹¹. In the US, more than 1 million people have Lewy body dementia⁸.

Why the right diagnosis matters

People with DLB can have a serious reaction to antipsychotic medicines, more so than people with other types of dementia⁶. Up to half of people with DLB who take these drugs can have severe reactions^{6, 7}. That is why the DLB diagnosis, not just 'dementia', should be clearly recorded in a person's notes, and new doctors should know about it⁶.

There is currently no cure for DLB, but some treatments can help manage symptoms for a while⁶. Early recognition, diagnosis and treatment can improve quality of life, says the Lewy Body Dementia Association⁹.

Where to find help

If this sounds familiar, talk to a doctor. In the UK, Alzheimer's Society dementia advisers are on 0333 150 3456⁴. In the US, the Alzheimer's Association runs a 24/7 Helpline on 800-272-3900⁷, and the Lewy Body Dementia Association's Lewy Line is 800-539-9767⁸.