Blog #16 Human Brains are growing!?

I’d like to introduce a new study＊１ conducted in the U.S and published last month. The study’s focus is on our brain volume.

The researchers used brain MRI (magnetic resonance imaging) from the participants in the Framingham Heart Study, which is a community-based population study that began in 1948 in Framingham, Massachusetts to investigate cardiovascular and other diseases. This study has continued for 75 years and involved second and third generations of the participants today.  This particular brain study cohort consisted of 3226 participants with an average age of 57.7 years at the time of their MRI.  A total of 1706 participants were female (53%) and 1520 (47%) were male. The birth decades ranged from the 1930s to 1970s. Those who had prevalent dementia, stroke, or other significant neurological disorder (eg, multiple sclerosis) at the time of the MRI were not included in this study. 

What the researchers found is very compelling and interesting—the participants born in the 1970s had 6.6% larger brain volumes (Intracranial volume) and almost 15% larger brain surface area (cortical surface area) than those born in the 1930s.  The participants born in the 1970s had 7.7% larger volume for white matter, 2.2% larger volume for cortical gray matter, 5.7% larger hippocampal volume, compared to those born in the 1930s.  And this is the result, of course, after they adjusted the height, sex, and age.  So yes, their brains are getting bigger!

There is a report that although the number of people with Alzheimer’s is rising with America’s aging population, the percentage of the population affected by the disease is actually decreasing. And the authors of this study hypothesize that improved brain development and size may actually be one of the reasons why.

I do believe that this study is very intriguing and has a possible and ongoing significance. However, as the authors of this study admitted and well described, there are some quite serious limitations.  The participants of this study cohort are predominately non-Hispanic White people. And they are healthy and well educated—almost half of the individuals (46%) achieved some college education.   Therefore, they don’t represent the broader US population.  Exclusion of people of color is often the case with the research for Alzheimer’s disease and other forms of dementia.  As the authors mentioned in the study, people of color experience more socioeconomic and health disparities in the US.  We don’t know how these stress and risk factors may affect brain health and development.  

Again, this is still a very valuable study, and I do hope to see more studies from now on involving people of color, people from LGBTQ+ communities, and people from disadvantaged communities.  These are also the same population of people who make up the U.S. , Right?  So, in that case, they absolutely need to be included.  And research communities need to make an effort to do so.

*1 DeCarli C, Maillard P, Pase MP, et al. Trends in Intracranial and Cerebral Volumes of Framingham Heart Study Participants Born 1930 to 1970. JAMA Neurol. Published online March 25, 2024. doi:10.1001/jamaneurol.2024.0469