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someone is out to get them, that there are strangers living in the house, or that a spouse is having an affair or has been replaced by an identical imposter.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. For more on this sensitive issue see our 'Driving and dementia factsheet'.
Up to two-thirds of people with DLB have movement difficulties when the condition is diagnosed, and this number increases as DLB progresses. These symptoms are similar to those of Parkinson's disease, and include slow and stiff (rigid) movement with a blank facial expression.
The person's posture may be stooped and their walk may be shuffling. They may also have difficulty with their balance, and their limbs may sometimes tremble.
Movement problems are one reason why a person with DLB is particularly prone to falls.
Sleep disturbance is another common symptom of DLB and may start years before the diagnosis. Someone with DLB may fall asleep very easily during the day, but have restless, disturbed nights. In the most common night-time sleep problem, the person has violent movements (eg yelling, hitting out) as they try to act out nightmares. This is called rapid eye movement sleep behaviour disorder and is found in different Lewy body disorders such as DLB and Parkinson's disease. For bed partners it can be very distressing or even physically harmful.
Some people with DLB lose their sense of smell, become constipated or have urinary incontinence (passing urine when they don't intend to). They may also faint or have unexplained episodes when they lose consciousness for a few minutes.
DLB is a progressive condition. Over time, symptoms increase and get worse. This is generally over a period of several years.
As the disease progresses, problems with day-to-day memory and other mental abilities become more similar to those of middle- or later-stage Alzheimer's disease. People can also develop behaviours that challenge (eg agitation, restlessness, shouting out).
Worsening movement problems mean that walking gets slower and less steady. As a result, falls become more common. In the later stages of DLB, many people have problems with speech and swallowing, leading to chest infections or risk of choking.
Eventually, someone with DLB is likely to need a large amount of nursing care. How quickly the condition progresses and the life expectancy of a person with DLB vary a lot. On average someone might live for about six to 12 years after the first symptoms, similar to a person with Alzheimer's disease.