Is There Good News For Patients With Dementia? A Study Indicates That Human Brain Size Has Increased Over The Past 75 Years

The human brain has changed in size throughout millennia, but a new study discovered a notable rise in brain size between those born in the 1930s and those born in the 1970s. This larger brain, which is evident in surface areas, volume, and hippocampal structures, may be linked to better health and more opportunities for education. Researchers from UC Davis Health performed this new study, and JAMA Neurology just published the findings.

Some scientists have hypothesized that the human brain is decreasing during the course of human biology, which is measured in millions of years. This theory has been influenced, at least in part, by the knowledge that human bodies are becoming smaller. On the other hand, current research suggests that the brain’s volume grew during brief periods of time or by biological changes that occurred throughout generations. It may not seem like much, but that might be a helpful biological defense against dementia.

Major population studies carried out in the United States and Great Britain over the last several decades have shown a decline in the incidence, or amount, of new cases of dementia. Among these is the Framingham Heart Study, which began collecting data from Framingham, Massachusetts, citizens in 1948.

UT Health San Antonio neurologist Sudha Seshadri and colleagues’ 2016 research revealed that although the incidence of dementia has declined since the late 1970s, the total number of cases, or prevalence, has increased. “That was a piece of hopeful news,” says Seshadri.

“It indicated that the average age at which a person developed symptoms had increased over a 30-year period.”

The following outcomes astonished the team: Why was there a decreased chance of dementia? Even if the cardiovascular health of the Framingham residents and their children had improved over time, which influences the risk of developing dementia, this would not explain the whole decline. Moreover, the effect was limited to those with a high school diploma, which suggested—in Seshadri’s words—that changes in early life might be the root reason of heightened resistance to dementia.

Because the scientists reasoned that bigger brains would arise from increased health throughout development, they decided to examine if the brains of the Framingham people exhibited indications of these changes. The researchers had just begun using magnetic resonance imaging (MRI) for brain scans in 1999. Therefore, the researchers examined a subset of 3,226 individuals who had an MRI between the ages of 45 and 74 and were born between the 1930s and the 1970s.

After analyzing the MRI data, the researchers discovered that younger generations’ brain sizes have increased in a number of different parameters. From 1236 milliliters in 1930s births to 1317 milliliters in 1970s births, the intracranial volume, or brain volume, grew by 6.6%. This was determined by measuring the amount of space inside the skull.

In addition, the amount of the white matter and the hippocampus, a region crucial for memory processing, had increased. The cortex, the brain’s outermost layer, had expanded in surface area as well, but its thickness had dropped by over 20%.

The research’s lead author, Charles DeCarli of UC Davis, said that “larger brain structures like those observed in our study may reflect improved brain development and improved brain health.”

“A larger brain structure may buffer the late-life effects of age-related brain diseases like Alzheimer’s and related dementias and represents a larger brain reserve.”

The question of how diverse populations’ experiences of brain growth throughout generations is still open to debate. It’s unknown how living in less wealthy circumstances influences brain growth since the majority of non-Hispanic White research participants in the Framingham study were healthy, well-educated, and non-Hispanic.