New Delhi: Brains of people with dementia, alcohol addiction or psychiatric disorders such as schizophrenia may show accelerated ageing, with each condition leaving its own distinct patterns in specific areas of the brain, a study has found.
Scientists calculate how old the brain is relative to the body using 'predictive age difference' (PAD) — the difference between chronological age and the age predicted by brain imaging. A positive value indicates accelerated brain ageing.
Researchers, including those from Nanjing University of Aeronautics and Astronautics in China, collected structural magnetic resonance imaging (MRI) data from 45,900 healthy people across several brain imaging databases and compared them with data from 2,698 patients with different brain disorders and conditions.
The conditions analysed included attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), alcohol or tobacco addiction, Alzheimer's disease, mild cognitive impairment, schizophrenia, bipolar disorder and major depressive disorder.
The authors found that neurodegenerative disorders, Alzheimer's disease and mild cognitive impairment, had the strongest association with a high predictive age difference.
Addiction and psychiatric disorders were also associated with an increased predictive age difference, whereas the brains of people with ADHD or ASD showed no significant differences in PAD values compared with healthy participants.
"Results showed that while PAD was consistently greater across disorders, different brain disorders showed different degrees of abnormality, the highest effects in dementia, followed by addiction and psychiatric disorders, but not different from expected in developmental disorders," the authors wrote.
The researchers also examined PAD values in specific brain regions and analysed which genes showed increased expression in people with different brain disorders.
The prefrontal cortex, responsible for higher-level functions such as attention and decision-making, showed a higher PAD across brain disorders.
A higher predictive age difference in the frontal and temporal lobes, involved in executive function, voluntary movement and language comprehension, was associated with psychiatric disorders, while a high value in the frontal and occipital cortex, which is involved in visual processing, was associated with dementia.
Addiction was linked to a high PAD in the default mode network, which is active during internally focused thought, among other brain regions.
While the findings are correlational rather than causal, and conditions such as psychiatric disorders and addiction often occur together, the authors suggested that understanding predictive age difference could help identify biomarkers for common brain disorders.
They added, "Different neurological disorders appear to leave different signatures on the brain ageing clock, which may help researchers better understand the neural and biological pathways involved in these conditions."