Victims can often grow grumpy when they become forgetful, and may take it out on their loved ones.

'Can you imagine how it feels when you are accused of stealing by a [dementia-affected] spouse - who can't find what he or she is looking for - after 40 years of marriage?' he said.

In Hong Kong, the need is clearly growing: dementia has overtaken diabetes to move on to the list of the city's top five killers among non-communicable conditions, after cancer, heart diseases, stroke and chronic lower respiratory disease.

Last year, 767 people were killed by dementia-related diseases in Hong Kong while 522 died from diabetes. But dementia's toll might actually be higher, because the cause of death is often attributed to other diseases such as pneumonia.

Dementia is not a disease but a syndrome caused by a number of brain disorders - most commonly Alzheimer's disease.

Although dementia is not curable, regular exercise can help prevent the onset of the condition, and treatment and care can greatly improve patients' quality of life, Yeoh said.

Dr Jimmy Wu Yee-ming, chairman of the Hong Kong Alzheimer's Disease Association, said while Hong Kong boasts about its world-class health care system, few resources are being used to raise public awareness of the condition. While publicity is given to some celebrity victims, such as academic Dr Charles Kao Kuen, the father of fibre optics, much work remains to be done at the community level, and there is little government support, he said.

A recent study showed that as few as 30 per cent of doctors said they were confident about diagnosing dementia and only 21.7 per cent were confident about handling patients with Alzheimer's disease. A 2007 study showed that just one in 10 victims of Alzheimer's were formally diagnosed with the condition.

Yeoh said it was time for the government to act, since dementia was officially recognised as an important cause of death - which puts a heavy burden on health care systems - by the United Nations in September.

Better understanding can also help in systematic analyses of the condition's impact, and help policy makers set up prevention strategies and measures to help sufferers.

'If you want to promote healthy ageing - and dementia is something you can't prevent but you can mitigate its impact - you should do it, even though it's not curable,' he said.

An estimated 10 per cent of the population over 60 years of age has been diagnosed with dementia. In Hong Kong dementia is often confused with Alzheimer's disease, which is a key cause of the condition.

In response to the UN's recognition of the heavy mortality caused by dementia, the health department said the government would abide by international standards in setting out its policies on various diseases.

6

The number of months dementia must be present before it can be diagnosed

- Alzheimer's disease first identified in 1901