Thin cerebral cortex linked to dementia

Individuals with thinner regions of the brain’s cerebral cortex are more likely to show early evidence of dementia, the study found.

Scientists looked at Magnetic Resonance Imaging (MRI) scans of the brains of 159 cognitively normal older people.

Three years later test results from 125 participants showed 21 per cent of those with a thinner cerebral cortex showed signs of mental decline.

The same pattern was seen in seven per cent of volunteers with a cortex of average thickness. Among volunteers with a thicker than average cortex there was no evidence of mental decline.

The cerebral cortex is the outer layer of the cerebrum, the most highly developed part of the brain where processing of muscle control, sensory perceptions, memory, emotions and speech take place. Cerebral cortex thickness can vary from about 1.5 millimetres to 5 millimetres.

The researchers also looked at cerebrospinal fluid (CSF) samples from 84 participants after three years to check levels of amyloid protein, a hallmark of Alzheimer’s. They found that 60 per cent of people with a thinner cortex had abnormal CSF amyloid levels similar to those with Alzheimer’s. This compared with 36 per cent of those with average cortical thickness and 19 per cent of those with an unusually thick cortex.

The research at Massachusetts General Hospital and the University of Pennsylvania is published online in Neurology.

It adds to evidence suggesting brain shrinkage predates early symptoms of Alzheimer’s.

Dr Simon Ridley, from Alzheimer’s Research UK, said: “The ability to predict who will develop Alzheimer’s is a key target for dementia research, as it would allow new treatments to be trialled early, when they are more likely to be effective.”