The City of Edinburgh Council has launched a dementia awareness campaign, in partnership with the local health board and charity Alzheimer Scotland.

Recognising the Signs is the campaign's title and this, the people of Edinburgh are being told, will be increasingly important, with cases of dementia in the city expected to rise by 65% in the next 20 years.

Only two out of every three people with dementia are believed to have been diagnosed. So people are being told to look out for symptoms in themselves or in others, such as short- term memory loss, unexplained anxiety or depression, or faulty thinking or reasoning such as finding it hard to follow TV or conversations.

But the under-diagnosis of dementia is a puzzle to the authorities that poses challenging questions. The 66% diagnosis rate is quite high. In England the rate is under 50% and some charities believe the true rate in Scotland may be closer to that. It used to be lower still. The evidence of past campaigns like Edinburgh's is that they have mixed results and rates of diagnosis remain stubbornly low.

Many people with dementia are diagnosed very late or die without ever having the condition identified.

One reason for this is that a diagnosis can be very difficult to make and some of the symptoms, such as memory loss, can be a result of age, not dementia, or of other conditions including stress.

There are also lots of reasons why people would not come forward earlier when they have worrying symptoms.

A dementia diagnosis is a scary one. It is regarded as a terminal illness and there is a considerable fear factor. Sometimes people take the view that the symptoms are a normal part of ageing, and nothing can be done.

There is also still a considerable stigma attached to dementia, which many would like to see wiped out. There is some debate in the medical profession about the value of early diagnosis.

Screening for symptoms has been particularly controversial, because there is little that medicine can do to stave off the illness when it is identified early. However, medical interventions may not be the only worthwhile response to dementia.

People cannot be forced to come forward but a diagnosis could be made more useful with more post-diagnostic support, experts believe. Improving such support and other measures to make communities more dementia friendly are already part of the Scottish Government's updated dementia strategy.

Human interaction has also been described as the equivalent of chemotherapy for dementia. This is seen in the remarkable success of programmes like Scotland's own football reminiscence schemes.

Edinburgh's campaign will include advertising, web information and leaflets designed to help people recognise symptoms, as well as highlighting support on offer.

Edinburgh aims to become an official "dementia friendly" city. Improving diagnosis rates and public understanding of the illness may go hand in hand. It will be interesting to see how effective the campaign is in cracking this chicken-and-egg challenge.