Brain Volume Increasing Among People Born in More Recent Decades

Participants born in more recent decades vs those born in earlier decades show trends of larger brain volumes, which may potentially explain the decline in incident dementia, according to study findings in JAMA Neurology. 

With the increase in the aging population due to improvements in therapeutics, it is expected that the incidence of neurodegenerative diseases, including Alzheimer disease (AD) and dementia, to increase accordingly. However, the Framingham Heart Study (FHS) results report that dementia incidence is on the decrease.

Researchers conducted a cross-sectional study to determine if early life health impacts brain development, as shown through measurements of intracranial and regional brain volumes. The FHS included 5209 participants born in 1930 through 1970 without dementia from Framingham, Massachusetts. 

A total of 5060 individuals who underwent magnetic resonance imaging (MRI) were included in the study. To reduce variability in MRI readings, the researchers conducted a subgroup analysis with 4647 individuals imaged on the same 2 scanners.

Some study outcomes include height, volumes of different brain areas, cortical surface area, and cortical thickness. 

The final analysis included 3226 individuals (average age, 57.4; women, 53%) at the time of MRI. The median birth decade was the 1950s, with a range from 1930 to 1970. Nearly half of all participants had some level of college education (46%). 

At baseline, there were significant differences for patients of female sex vs male sex for:

• height (-5.5 in),
• intracranial volume (-155.0 mL),
• hippocampal volume (-0.64 mL),
• cortical surface area (-264 cm²),
• total cortical gray volume (-53.5 mL), and
• white matter volume (-63.3 mL).

The following observations were reported for patients born in the 1970s compared with those born in the 1930s:

• 6.6% greater intracranial volume (1234 mL; 95% CI, 1220-1248 vs 1321 mL; 95% CI, 1301-1341);
• 7.7% greater white matter volume (441.9 mL; 95% CI, 435.2-448.5 vs 476.3 mL; 95% CI, 467.0-485.7); 
• 5.7% greater hippocampal volume value (6.51 mL; 95% CI, 6.42-6.60 vs 6.89 mL; 95% CI, 6.77-7.02);
• 14.9% greater cortical surface area value (1933 cm²; 95% CI, 1908-1959 vs 2222 cm²; 95% CI, 2186-2259).

There were no significant associations between sex and decade of birth. The researchers conducted a subgroup analysis with 1145 participants born within the 1940s (mean age, 60.0) and 1950s (mean age, 59.0), which revealed similar findings to the primary analysis.

Study limitations include conducting the study in a majority healthy and White patient population and the inability to determine causality.

“Early life environmental influences may explain these results and contribute to the declining dementia incidence previously reported in the Framingham Heart Study cohort,” the researchers concluded. 

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.