The UCL study also found that men tended to have older brains than women of the same age.
According to the study, higher brain age is associated with slightly worse scores on mental cognitive) tests, and also predicted increased brain shrinkage over the following two years.
Researchers suggest this could be an important indicator for people at risk of cognitive decline or other brain-related ill health.
“We found that despite people in this study all being of very similar real ages, there was a very wide variation in how old the computer model predicted their brains to be," said lead author Prof Jonathan Schott, of UCL Dementia Research Centre and UCL Queen Square Institute of Neurology.
“We hope this technique could one day be a useful tool for identifying people at risk of accelerated ageing, so that they may be offered early, targeted prevention strategies to improve their brain health.”
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The scientists used an established MRI-based model to estimate the brain age of people on the Alzheimer’s Research UK-funded Insight 46 study, led by Prof Schott.
As they had been a part of the study throughout their lives, scientists were able to compare their current brain ages to various factors from across the life course.
They were all between 69 and 72, but their estimated brain ages ranged from 46 to 93.
The study found that people with worse cardiovascular health at age 36 or 69 had worse brain health, as did those with increased cerebrovascular disease on MRI (relating to blood flow and blood vessels in the brain).
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“The Insight 46 study is helping reveal more about the complex relationship between the different factors influencing people’s brain health throughout their life," said Dr Sara Imarisio, head of research at Alzheimer’s Research UK.
“Using machine learning, researchers in this study have uncovered yet more evidence that poorer heart health in midlife is linked to greater brain shrinkage in later life.
“We’re incredibly grateful to the dedicated group of individuals who have contributed to research their entire lives making this work possible.”
The findings are published in The Lancet Healthy Longevity.