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Human brain size getting larger, has potential to cut dementia risk

The size of the human brain is getting larger and the bigger size may reduce the potential of overall age-related dementia, according to a study.

HQ Team

March 27, 2024: The size of the human brain is getting larger and the bigger size may reduce the potential of overall age-related dementia, according to a study.

Researchers at the University of California Davis Health found participants born in the 1970s had 6.6% larger brain volumes and almost 15% larger brain surface area than those born in the 1930s.

The researchers predicted the increased brain size may lead to an increased brain reserve, potentially reducing the overall risk of age-related dementias.

“The decade someone is born appears to impact brain size and potentially long-term brain health,” said Charles DeCarli, first author of the study.

Improved brain health

“Genetics plays a major role in determining brain size, but our findings indicate external influences — such as health, social, cultural and educational factors — may also play a role,” said DeCarli, a professor of neurology and director of the UC Davis Alzheimer’s Disease Research Center.

“Larger brain structures like those observed in our study may reflect improved brain development and improved brain health,” DeCarli said. “A larger brain structure represents a larger brain reserve and may buffer the late-life effects of age-related brain diseases like Alzheimer’s and related dementias.”

The community-based study began in 1948 in Framingham, Massachusetts, to analyze patterns of cardiovascular and other diseases. The original Framingham Heart Study had a cohort of 5,209 men and women between the ages of 30 and 62.

The research, using brain magnetic resonance imaging, has continued for 75 years and now includes second and third generations of participants.

The imaging was conducted between 1999 and 2019 with FHS participants born during the 1930s through the 1970s. The brain study consisted of 3,226 participants (53% female, 47% male) with an average age of about 57 at the time of the MRI.

1930s vs 1970s

The research led by UC Davis compared the MRIs of people born in the 1930s to those born in the 1970s.

It found gradual but consistent increases in several brain structures. For example, a measure that looked at brain volume (intracranial volume) showed steady increases decade by decade. 

For participants born in the 1930s, the average volume was 1,234 millilitres, but for those born in the 1970s, the volume was 1,321 millilitres, or about 6.6% greater volume.

Cortical surface area — a measure of the brain’s surface — showed an even greater increase decade by decade.

Participants born in the 1970s had an average surface area of 2,104 square centimetres compared to 2,056 square centimetres for participants born in the 1930s — almost a 15% increase in volume.

Grey matter, hippocampus

The researchers found brain structures such as white matter, grey matter and hippocampus (a brain region involved in learning and memory) also increased in size when comparing participants born in the 1930s to those born in the 1970s.

According to the Alzheimer’s Association, approximately 7 million Americans are currently living with Alzheimer’s disease. That number is expected to rise to 11.2 million by 2040.

Although the numbers are rising with America’s ageing population, the incidence of Alzheimer’s — the percentage of the population affected by the disease — is decreasing.

previous study found a 20 per cent reduction in the incidence of dementia per decade since the 1970s. Improved brain health and size may be one reason why.

The findings were published in JAMA Neurology.


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