More than 1,000 people across North Somerset may be living with undiagnosed dementia, according to estimates by the NHS.

GPs’ figures show there are 2,119 people over-65 who have been diagnosed with some form of dementia, but estimates based on the age profile and gender of patients suggest the real figure may be more than 3,300.

The figures are being collected by the NHS in response to the Prime Minister’s Challenge on Dementia set up by Theresa May’s predecessor David Cameron.

Dementia patients can suffer from a loss of memory, behaviour changes and problems in reasoning.

The most common cause of dementia is Alzheimer’s, which accounts for about 60 per cent of cases, but it can be the result of brain damage caused by a stroke or neurological conditions such as Parkinson’s.

Dementia can affect anyone at any age and across the country there are approximately 800,000 people believed to have the condition.

The vast majority of cases involve older people and after the age of 65 the likelihood of dementia doubles every five years.

This peaks for men in their early-80s when a quarter suffer from dementia, whereas the women it is when they are in their late-80s when the rate reaches 27 per cent.

North Somerset has a number of support groups, while events such as the bi-monthly memory café run by Portishead Rotary also are helpful.

The Bristol, North Somerset and South Gloucestershire Clinical Commissioning Group has advice on its website for those diagnosed and their families, and also advises people to go to their GP if they fear they might have dementia.

The Alzheimer’s Society said getting a diagnosis allows people with dementia to access emotional, practical, legal and financial advice, as well as any support and treatment available.

The society’s senior policy officer, Andrew Boaden, said: “Dementia diagnosis rates vary significantly from place to place, which is concerning.

“Alzheimer’s Society research shows that over a third of people with dementia in the UK don’t get a formal diagnosis, and we believe everyone with dementia has a right to know.

“With the number of people with dementia set to reach one million by 2021, the Government and the NHS must do more to address this issue.”