A global study predicts the number of people with dementia will nearly triple by 2050.
The World Alzheimer Report estimates 60,000 New Zealanders have dementia, and that number will increase in the next 35 years to more than 150,000.
It said the total cost of dementia to Australasia had increased by 40 percent in the last five years, higher than the global average of 35 percent.
Alzheimers New Zealand's director Catherine Hall said the country should develop a national dementia plan to ensure people get the help they needed.
"That plan needs to bring together all of the organisations and parts of the dementia sector so that we're delivering the care and support that people with dementia need now so we're ready to deliver the care and support that will be needed in the future as the numbers increase," she said.
Ms Hall said reducing the costs of dementia depended on making improvements to the public health system and finding more effective treatments for Alzheimers.
Ministry of Health geriatrician Dr Phill Wood said there had not been any new method for treating dementia for 20 years, and people should focus on early diagnosis and lifestyle.
Dr Wood, who is involved in the Brain Research Centre, said he was disappointed with the progress of medication, and he was focussing on the relationship between lifestyle and dementia.
"Most of the research that's going on at the moment is primarily around lifestyle, diet, education, exercise, all of those known things," he said.
"I think the challenge will be finding better mechanisms to put those things together and make them work together."
The World Alzheimer Report estimated 46.8 million people worldwide were living with dementia, and that someone developed the condition every three seconds.
It predicted the number would almost double every 20 years, reaching 74.7 million in 2030 and 131.5 million in 2050.
Global costs of dementia were increasing, it said, from $US604 billion in 2010 to $US818 billion in 2015.