As with most types of dementia, the first symptoms of DLB may affect someone only slightly, but gradually they get worse and cause problems with daily living.

Everyone is different, but a person with DLB will usually have some of the symptoms of Alzheimer's disease and some of the symptoms of Parkinson's disease. They will also have some symptoms which are unique to DLB. These are covered in the sections below.

Problems with mental abilities

Problems with attention and alertness are very common in DLB. An important feature of the condition is that these problems may switch between being bad and then better - or the other way round - over the course of the day, by the hour or even a few minutes. Someone with DLB may stare into space for a long time or have periods when their speech is disorganised.

People may also have difficulties judging distances and seeing objects in three dimensions. It is common to struggle with planning, organising and decision-making. Some people also experience depression. Day-to-day memory is often affected in people with DLB, but usually less in the early stages than in early Alzheimer's disease.

Hallucinations and delusions

Visual hallucinations (seeing things that are not there) occur frequently in people with DLB, often in the early stages of the condition. They can happen daily.

Visual hallucinations are often of people or animals, and are detailed and convincing to the person with dementia. They can last several minutes and may be distressing. (Someone may also have visual misperceptions, such as mistaking a shadow or a coat on a hanger for a person.)

Auditory hallucinations - hearing sounds that are not real, such as knocking or footsteps - can happen but are less common.

Hallucinations and visual misperceptions partly explain why most people with DLB have delusions (persistently thinking things that are not true) at some stage.

Some common delusions held by people with DLB are believing that someone is out to get them, that there are strangers living in the house, or that a spouse is having an affair or has been replaced by an identical imposter. The person's relatives and carers may find these delusions very distressing.

Visual hallucinations are also a common reason for a person with DLB to stop driving, because it is no longer safe for them to be on the road.