Dementia is not a disease itself. It's a collection of symptoms that result from damage to the brain caused by different diseases, such as Alzheimer's. These symptoms vary according to the part of the brain that is damaged.

Different types of dementia can affect people differently, and everyone will experience symptoms in their own way.

However, there are some common early symptoms that may appear some time before a diagnosis of dementia. These include:

• memory loss
• difficulty concentrating
• finding it hard to carry out familiar daily tasks, such as getting confused over the correct change when shopping
• struggling to follow a conversation or find the right word
• being confused about time and place
• mood changes

These symptoms are often mild and may get worse only very gradually. It's often termed "mild cognitive impairment" (MCI) as the symptoms are not severe enough to be diagnosed as dementia.

You might not notice these symptoms if you have them, and family and friends may not notice or take them seriously for some time. In some people, these symptoms will remain the same and not worsen. But some people with MCI will go on to develop dementia.

Dementia is not a natural part of ageing. This is why it's important to talk to a GP sooner rather than later if you're worried about memory problems or other symptoms.

The most common cause of dementia is Alzheimer's disease. Common symptoms of Alzheimer's disease include:

• memory problems, such as regularly forgetting recent events, names and faces
• asking questions repetitively
• increasing difficulties with tasks and activities that require organisation and planning
• becoming confused in unfamiliar environments
• difficulty finding the right words
• difficulty with numbers and/or handling money in shops
• becoming more withdrawn or anxious

Find out more about Alzheimer's disease.

Vascular dementia is the second most common cause of dementia, after Alzheimer's. Some people have both vascular dementia and Alzheimer's disease, often called "mixed dementia".

Symptoms of vascular dementia are similar to Alzheimer's disease, although memory loss may not be as obvious in the early stages.

Symptoms can sometimes develop suddenly and quickly get worse, but they can also develop gradually over many months or years.

Specific symptoms can include:

• stroke-like symptoms: including muscle weakness or temporary paralysis on one side of the body (these symptoms require urgent medical attention)
• movement problems – difficulty walking or a change in the way a person walks
• thinking problems – having difficulty with attention, planning and reasoning
• mood changes – depression and a tendency to become more emotional

Find out more about vascular dementia.

Dementia with Lewy bodies has many of the symptoms of Alzheimer's disease, and people with the condition typically also experience:

• periods of being alert or drowsy, or fluctuating levels of confusion
• visual hallucinations (seeing things that are not there)
• becoming slower in their physical movements
• repeated falls and fainting
• sleep disturbances

Find out more about dementia with Lewy bodies.

Although Alzheimer's disease is still the most common type of dementia in people under 65, a higher percentage of people in this age group may develop frontotemporal dementia than older people. Most cases are diagnosed in people aged 45-65.

Early symptoms of frontotemporal dementia may include:

• personality changes – reduced sensitivity to others' feelings, making people seem cold and unfeeling
• lack of social awareness – making inappropriate jokes or showing a lack of tact, though some people may become very withdrawn and apathetic
• language problems – difficulty finding the right words or understanding them
• becoming obsessive – such as developing fads for unusual foods, overeating and drinking

Find out more about frontotemporal dementia.

As dementia progresses, memory loss and difficulties with communication often become severe. In the later stages, the person is likely to neglect their own health, and require constant care and attention.

The most common symptoms of advanced dementia include:

• memory problems – people may not recognise close family and friends, or remember where they live or where they are
• communication problems – some people may eventually lose the ability to speak altogether. Using non-verbal means of communication, such as facial expressions, touch and gestures, can help
• mobility problems – many people become less able to move about unaided. Some may eventually become unable to walk and require a wheelchair or be confined to bed
• behavioural problems – a significant number of people will develop what are known as "behavioural and psychological symptoms of dementia". These may include increased agitation, depressive symptoms, anxiety, wandering, aggression, or sometimes hallucinations
• bladder incontinence is common in the later stages of dementia, and some people will also experience bowel incontinence
• appetite and weight loss problems are both common in advanced dementia. Many people have trouble eating or swallowing, and this can lead to choking, chest infections and other problems.

Find out more

• Find dementia information and support services
• Get dementia information emails from the NHS Dementia Information Service
• Communicating with someone with dementia
• Coping with behavioural changes with dementia
• Alzheimer's Society: eating and drinking