One in three people born this year will develop dementia, according to new figures.
The Alzheimer's Research UK charity warned of a "looming national health crisis" as the population ages.
It called for greater efforts across the globe to help develop new treatments.
Dementia affects 850,000 people in the UK, resulting in the loss of brain cells. The most common type is Alzheimer's disease.
Early symptoms include problems with memory and thinking. As the disease progresses, people can experience difficulty with walking, balance and swallowing.
Alzheimer's Research UK said age was the biggest risk factor for developing dementia.
As people live longer than ever before, the numbers with dementia will rise.
The latest analysis, commissioned by the charity and carried out by the Office of Health Economics, was released to mark World Alzheimer's Day.
It showed 27% of boys born in 2015 will develop the condition in their lifetime, alongside 37% of girls.
Previous research from the same team has estimated that the development of a drug which could delay the onset of dementia by five years would cut the number of cases by a third.
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Dr Matthew Norton, head of policy at Alzheimer's Research UK, said: "It's wonderful news that each generation is living longer than the last, but it's important to ensure that people can enjoy these extra years in good health.
"Dementia is our greatest medical challenge and, if we are to beat it, we must invest in research to find new treatments and preventions.
"Research has the power to transform lives, and our actions now will help determine the future for children born today."
Amanda Franks, from Swindon, a champion of Alzheimer's Research UK, whose mother Cathy was diagnosed with early-onset Alzheimer's six years ago, said: "My mum was only 58 when she was diagnosed.
"Up until then, we had no idea this devastating disease could affect someone so young.
"Simple day-to-day tasks like making a cup of tea, getting dressed and eating soon became a huge challenge for mum.
"Dad cared for her at home with family help for five years, by which time things were getting out of hand with her violent behaviour and hallucinations - life became extremely stressful.
"As a mum myself, I would dearly love to see preventions and new treatments found to defeat Alzheimer's disease and other dementias, giving hope to people now and future generations."
Also to mark World Alzheimer's Day, the Alzheimer's Society urged people to sign up to become a dementia friend.
The initiative combines face-to-face information sessions and online videos to help people learn more about dementia and ways they can make a difference.