The National Centre for Social and Economic Modelling found the number of Australians over 50 diagnosed with the disease is expected to increase by 73 per cent, from 153,888 in 2021 to 266,114 in 2041.

The annual cost to the economy is expected to rise from $15.5 billion to $26.6 billion over that time period.

The burden on residential, community-based and informal care is expected to grow with the rising caseload.

The cost of residential care is expected to reach $6.8 billion, formal community care $1.8 billion and the cost of replacing informal care would grow to $16.2 billion.

The number of people living with Alzheimer's disease in residential care is expected to increase to 73,172 while the number living in the community will grow to 192,942.

However, the modelling found if a hypothetical disease-modifying therapy was able to delay the onset of the disease and prevent some patients from developing moderate or severe symptoms, it could save $8.159 billion in direct costs and $4.718 billion in indirect costs.

Lead author Emeritus Professor Laurie Brown said the modelling gave a compelling argument to invest in prevention and early intervention therapies.

"I think as a community we have to say, 'What's our willingness to pay for those types of interventions'?" Emeritus Professor Brown said.

"So if I'm going to develop Alzheimer's disease, I'd much rather live many years with milder Alzheimer's disease, which is going to have some impact but not those extensive burdens, rather than progressing on to more moderate or severe dementia."

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Emeritus Professor Brown said the hypothetical therapy was based on an approved therapy in the United States and other modelling projects within the literature.

"If you have mild dementia, your risk of being in residential aged care is less and the demand for informal care from your partner or family members or friends is much less."

Alzheimer's disease is the most common form of dementia, which affects 75 per cent of all people aged 65 and older who have dementia.

The report found two-thirds of primary carers of people living with severe dementia provide 60 or more hours of care each week, while those caring for patients with moderate disease averaged 42 hours. The work of informal carers in 2021 was valued at $9.4 billion.

The Economic and Societal Cost of Alzheimer's Disease in Australia 2021-2041 report was commissioned by Biogen Australia and New Zealand.