England's top doctor has urged people to look out for new symptoms in older loved ones when they gather for Christmas.

Some 499,068 people now have a dementia diagnosis - an increase of 19,416 from this time last year.

Around two thirds of sufferers aged over 65 are thought to have been diagnosed, but thousands more are still living with dementia without accessing all the support available.

Dr Jeremy Isaacs, England national clinical director for dementia, said symptoms often develop slowly and people should be alert to changes in relatives they haven't seen for a while.

He added: "There are lots of reasons why people might be forgetful or absent-minded at such a busy time of the year, but it could also be the sign that something is wrong.

"Issues that may not have been obvious previously such as forgetfulness, difficulty making plans, or word-finding problems can come to the surface or be easier to spot when families or friends across the country get together over the festive season."

Getting a diagnosis is the first step towards accessing a wide range of NHS services, Dr Isaacs said.

He added: "If you have noticed that someone has symptoms, please encourage them to visit their GP for an assessment - the sooner someone is seen the quicker the NHS can help."

Subtle changes in his behaviour were among the first signs that something was wrong for Dr Matthew Alexander, 79.

The former GP's wife of more than 50 years, Sara, 73, remembers a particular incident when he became confused for around five minutes.

She said: "We were sitting around the table and it was like suddenly he was in a different place. It's hard to explain, he was saying things which had no meaning, confusing everything."

Dr Alexander had recently undergone surgery to remove a liver tumour the size of an orange, and at first his family thought the confusion may have been linked to his recovery.

Sara and the couple's two children kept a close eye on him. On another occasion, he suffered an unexpected fall in the house and had to be taken to hospital in an ambulance.

"It was all just so unnatural, small, small things," Sara said. "I never thought of dementia, that word wasn't in my vocabulary. I just thought, 'something is wrong'."

Sara became determined to discover the cause of her husband's unusual behaviour and arranged for them to visit a memory clinic.

But shortly before he was due to undergo tests, his cancer was found to have recurred. Doctors felt the stress may interfere with the results so he remained undiagnosed, and then the struck.

Dr Alexander finally received a diagnosis of vascular dementia and in May this year.