The Brain Chart study, led by Cambridge University, is the first to identify milestones that can potentially be used to assess whether brains are “ageing healthily”. The chart shows how the brain expands rapidly in early life — by 70 per cent from about a third of the way through pregnancy to the age of three years — and shrinks slowly as we age.
The volume of grey matter (or brain cells) increased rapidly in the womb and peaked before the age of six. The amount of white matter, or “brain connections” that affect learning and brain functions, also increases rapidly from mid-pregnancy but peaks before 29.
Grey matter in the subcortex, which controls bodily functions and basic behaviour, peaks in adolescence at the age of 14 and a half while the decline in overall white matter volume begins to accelerate after the age of 50. This will help to determine whether individuals are on a standard trajectory.
At present, no reference standard exists — in contrast to the growth charts for a child’s height, weight and head circumference that have been a cornerstone of healthcare for more than 200 years. It means that there are now reference points for irregular brain structure, which are likely to be of use in assessing neurological and psychiatric disorders and brain diseases.
The brain charts confirmed that while size decreases naturally with age, it does so much faster in Alzheimer’s patients.
Researchers collated data from 123,984 MRI brain scans of 101,457 people, from a three-month-old foetus to a 100-year-old, from more than 100 studies worldwide. Their findings were published in the journal Nature.
Dr Richard Bethlehem, from the department of psychiatry at the University of Cambridge, said: “It’s allowed us to measure the very early, rapid changes that are happening in the brain, and the long, slow decline as we age. The charts are beginning to provide interesting insights into brain development, and our ambition is that, as we integrate more datasets and refine the charts, they could eventually become part of routine clinical practice.
“You could imagine them being used to help evaluate patients screened for conditions such as Alzheimer’s, for example, allowing doctors to spot signs of neurodegeneration.”
Co-lead researcher Dr Jakob Seidlitz from the Lifespan Brain Institute at Children’s Hospital of Philadelphia, said creating the brain charts involved “multiple technical feats” to extract data from MRI scans.
He said: “With brain imaging data, things are a bit more complicated than just taking out a measuring tape and recording someone’s height.”
Dr Bethlehem said: “The NHS does millions of brain scans every year and in most cases they are assessed by radiologists or neurologists relying on their expertise to judge whether there is anything clinically relevant apparent.
“We hope that clinicians in future will be able to compare their data against ours and produce a more comprehensive report adding additional objective and quantitative observations. This should effectively allow the neurologist to answer the question ‘this area looks atypical but atypical by how much?’”