'My husband suddenly suffered dementia in his early 50s.'

Lyne Hansen from near Darwin has just celebrated her 40th anniversary with her husband Mark.

But the event was a sad reminder of what she lost about a decade ago, when “all of a sudden, this person that I grew up with and we both knew each other very well, was gone”.

“There’s no longer any empathy, sympathy or compassion,” she said.

Mark suffers from frontotemporal dementia, a form of younger onset dementia, which initially affects behaviour, language and then memory.

A quarter of a million Australians suffer from younger onset dementia, with about one in 13 dementia sufferers under the age of 65, and some in their 40s, 30s and even their 20s, according to Alzheimer’s Australia.

Ms Hansen started seeing the signs of dementia in Mark in his early 50s.

His personality changed and their relationship suffered.

"The personality is eroded away early in the piece, and so, it's very sinister and you don't actually notice until there are big changes," she said.

"By that time you no longer have a good relationship with the person that has the disease."

She recalled a family outing to a restaurant, where Mark could not remember what a prawn was.

"He was starting to use different words for things and they didn't make sense. And we were starting to have arguments," she said.

It took several specialist appointments to correctly diagnose Mark, though he still will not believe there is anything wrong with him.

"The problem with people like Mark is they're fit, strong and healthy, but they just lose their ability," Ms Hansen said.

'People think dementia is only a disease of the elderly'

Professor of Ageing and Mental Health at University of New South Wales Henry Brodaty said younger onset dementia sufferers face unique challenges, since they often have young families and are still working and physically active.

As such, Professor Brodaty said diagnosis and care were insufficient.

"It's inadequately recognised. People think of dementia as only being a disease of older people," Professor Brodaty said.

"We've certainly become a lot more aware of it. We've become a lot more aware of the gaps these people face.

"They face gaps in diagnosis, gaps in helping them cope with this and their families in particular."

The Key Worker Program is the only specialised one-to-one support service for people with dementia under 65 (the national retirement age) and their carers.

It is currently federally funded.

But experts and the frontline victims of dementia are concerned it will not be able to keep up with demand if it is rolled into the National Disability Insurance Scheme (NDIS) from July next year.

Dementia numbers to triple by 2050

Graeme Samuel, the former head of the Australian Consumer and Competition Commission, is also concerned about the program.

He watched his mother die from Alzheimer's.

"It was quite devastating," Mr Samuel said.

"We went through the terrible journey she went through. We watched her decline."

It inspired him to become the president of Alzheimer's Australia.

He has been lobbying the Federal Government to respond to concerns about the Key Worker Program.

"That program is gathering pace and we hope will continue to be funded and gather pace because it provides very specialised care for people who are sometimes in their mid-20s and 30s," he said.

He said it would have significant disadvantages if rolled into the NDIS.

"The Government is working with Alzheimer's Australia to find a solution and preserve the unprecedented individuality and personal nature of the Key Worker Program."

Mr Samuel said it was imperative to invest in programs now, given the projected burden dementia will cause in the future.

Dementia currently costs the economy $6 billion a year and by 2050 the number of sufferers is tipped to almost triple to 900,000 people.

Mr Samuel said the recent federal budget put aside $200 million over five years into Alzheimer's research, but further investment remained a national health priority.

Professor Brodaty said scientists were focusing more on younger onset dementia and have developed early screening processes to detect the disorder.

"In most of the dementias it's a slow process," he said.

"In Alzheimer's it's estimated it takes 20 to 30 years of build-up in pathology in the brain before it becomes manifest.

"It's like a person may be cooking a disease, or building it up in their brain and are unaware of it until it reaches a threshold."

For Lyne Hansen, this is a small sign of hope.

"I've lost hope for Mark and for his generation," she said.

"But I have hope for the next generation. I hope diagnosis will happen earlier."

This post originally appeared on the ABC and was republished here with full permission. 

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