People with dementia, mild cognitive impairment, alcohol addiction, or psychiatric disorders such as schizophrenia show increased brain aging in specific patterns within the brain, according to a study published July 21 in PLOS Medicine by Shile Qi from the Nanjing University of Aeronautics and Astronautics, China, and colleagues.
The study examined how certain conditions can accelerate brain aging. Scientists use the predictive age difference (PAD) to measure how old the brain appears compared to a person's actual age. A positive PAD indicates that aging is accentuated or increased. The researchers collected structural magnetic resonance imaging data from 45,900 control subjects across several imaging banks and compared them with data from 2,698 patients diagnosed with various brain conditions and differences. These included attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), alcohol or tobacco addiction, Alzheimer's disease (AD), mild cognitive impairment (MCI), schizophrenia, bipolar disorder, or major depressive disorder.
According to the authors' findings, neurodegenerative disorders such as Alzheimer's disease and mild cognitive impairment had the largest association with a high PAD. Addiction and psychiatric disorders were also linked to increased PAD values. However, there were no significant differences in PAD between individuals with ADHD or ASD when compared to controls.
Further analysis looked at PAD values within specific regions of the brain and explored which genes showed increased expression among people with different conditions. The prefrontal cortex exhibited higher PAD across multiple brain disorders. Psychiatric disorders were associated with higher PAD in the frontal and temporal lobes; dementia was connected to high PAD in both frontal and occipital cortex areas; addiction was linked to elevated PAD within the default mode network as well as regions like the salience network, putamen, and thalamus. Differences in gene transcription also correlated with specific conditions.
The results are correlational rather than causal; some conditions such as psychiatric disorders and addiction frequently co-occur, the authors said. The authors suggest that further understanding of predictive age difference could help identify biomarkers for common neurological conditions.
The authors add: "Different neurological disorders appear to leave different signatures on the brain aging clock, which may help researchers better understand the neural and biological pathways involved in these conditions."
