Researchers from Texas analyzed nearly thirty years of medical records and brain autopsies of 678 elderly nuns from the United States. They found that the size of the head may be related to the degree of risk of developing dementia. Women who had a smaller skull circumference had a significantly higher risk of dementia – even after taking other risk factors into account.
The authors were based on the so-called Nun Study, which began in 1991 and included Catholic nuns from seven American cities. The participants ranged in age from 75 to 102, with an average age of 83. They all lived a very similar way of life – they had the same type of housing, income, diet, access to health care and avoided alcohol and smoking. Nevertheless, seventeen percent of them developed dementia by the end of their lives.
Scientists have found that nuns with less education and a smaller head circumference were four times more likely to develop dementia than those with more education and a larger head circumference. At the same time, a smaller hippocampus, i.e. the area of the brain responsible for memory, was found more often in participants with dementia.
According to experts a smaller head and brain size means a smaller cognitive reserve, thus, fewer brain cells and connections that could compensate for age-related damage. Education, on the other hand, helps create more complex neural networks and strengthens connections between brain cells.
At the same time, scientists remind that approximately ninety percent of head growth occurs by the sixth year of life and the brain reaches about seventy-five percent of its adult size already in the first year of life. The average head circumference is approximately 55 centimeters for women and 57 centimeters for men.
