A Surprising Win for Those with Larger Heads? "Dementia Risk Rises Sharply with Smaller Head Size and Lower Education"

US Researchers Track 700 Nuns for 30 Years
Smaller Head Circumference and Lower Education Linked to Higher Dementia Risk

A study has found that head size and level of education are closely linked to the risk of developing dementia later in life. In a 30-year study tracking elderly nuns across the United States, groups with smaller head circumferences and lower levels of education were up to four times more likely to develop dementia compared to those with larger head sizes and higher education levels.

Brain MRI scan image unrelated to the article content. Pexels

According to the UK’s Daily Mail on January 2 (local time), researchers in Texas analyzed health records and post-mortem brain autopsy results of 678 Catholic nuns living in seven US cities, based on data from “The Nun Study,” which began in 1991. The participants ranged in age from 75 to 102, with an average age of 83.

The researchers noted that the nuns belonged to the same religious order, resulting in similar living environments, income, diet, and access to medical care, and that they had similar lifestyle habits, such as abstaining from alcohol and smoking.

At the start of the study, cognitive tests showed that 118 participants (17%) exhibited mild cognitive impairment, a precursor to dementia, while 80 met the diagnostic criteria for dementia. Among the 334 nuns tracked for 20 years after the study began, 39% experienced severe cognitive impairment.

Head Size and Education Level: Dementia Risk Up to Four Times Higher

The analysis revealed that participants with smaller head circumferences and lower education levels were four times more likely to be diagnosed with dementia compared to those with higher education and larger head sizes. However, having only one of these factors-either a smaller head size or lower education-did not significantly increase the risk of dementia.

Participants with dementia also tended to have smaller hippocampi, the brain’s memory center. The researchers explained that smaller head and brain sizes mean fewer brain cells overall, reducing the brain’s capacity to cope with age-related damage or pre-dementia changes.

Research Team: “Dementia Prevention Is a Lifelong Task”

In contrast, a larger head circumference typically indicates a larger brain, which provides greater “cognitive reserve” through more brain cells and neural connections. This means that even if some brain cells are damaged with age, it is more likely that cognitive function will be maintained.

Education was also identified as an important factor in building cognitive reserve. The learning process strengthens connections between brain cells and is associated with a higher likelihood of maintaining healthy habits such as a balanced diet, exercise, and not smoking.

The researchers emphasized that about 90% of head growth occurs before age six, and by the end of the first year of life, the brain reaches 75% of its adult size. This suggests that dementia prevention is not just an issue for old age, but requires management from infancy throughout the entire lifespan.

The research team stated, “The results of The Nun Study show that cognitive health and dementia prevention are lifelong tasks,” adding, “It is the environment and education long before symptoms appear-not after-that are important.”