Why do younger generations have bigger brains?

A new study has found younger generations have bigger brains, and they're continuing to get larger, which could be reducing the risk of overall age-related dementia.

The study, conducted by researchers at American academic health centre UC Davis Health and published in medical journal JAMA Neurology, found participants born in the 1970s had 6.6 per cent larger brain volumes and almost 15 per cent larger brain surface area than those born in the 1930s.

Charles DeCarli is the first author of the study, a professor of neurology and director of the UC Davis Alzheimer's Disease Research Centre.

He said: "The decade someone is born appears to impact brain size and potentially long-term 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.

"Larger brain structures like those observed in our study may reflect improved brain development and improved brain health.

"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."

MRI scans (a type of scan that produces detailed images of what the body looks like inside) of participants born during the 1930s through the 1970s were taken between 1999 and 2019.

A total of 3,226 participants, 53 per cent female and 47 per cent male, took part with an average age of 57 at the time of their MRI.

Results found consistent increases in several brain structures.

One measure that looked at brain volume showed steady increases decade by decade - participants born in the 1930s had an average volume of 1,234ml but for those born in the 1970s, they had an average of 1,321ml, a greater volume of 6.6 per cent.

Cortical surface area, which is the measure of the brain's surface, showed an even greater increase - participants born in the 1970s had an average surface area of 2,104cm2 compared to 2,056cm2 for participants born in the 1930s - almost a 15 per cent increase.

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 between the two groups.

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