Increased brain size and volume may underly reduction in dementia incidence

By Sravya Valiveti. This article was initially published in the 4/11/24 edition of our Concussion Update newsletter; please consider subscribing.

A recent study published in JAMA Neurology by DeCarli et al. found that brain volumes and brain size are becoming progressively larger––based on MRI brain imaging observations of participants born between 1930 and 1970. It is worth noting that the dataset was primarily derived from the Framingham Heart study participant cohort of 3,226 participants who had no dementia or history of stroke or other neurological disorders. The study team obtained the MRI data between 1999-2019. The study team investigated the impact of differences in cranial and brain volumes and cortical thickness on long-term brain health and later-life dementia risk in patients.

Based on MRI imaging data and other data measures, findings revealed significant trends for brain size, i.e., larger intracranial, hippocampal, and white matter volumes and cortical surface area in those born during the latter decades, suggesting improved brain development. It is worth highlighting that the research team found significant findings: 6.6% greater intracranial volume, 7.7% greater white matter volume, and 5.7% greater hippocampal volume in those who were born in the 1970 decade when compared with the brain volumes of those born in the 1930 decade. DeCarli acknowledges that both genetic and external factors such as early environment, education level, and lifestyle influences form the underlying basis of human brain development, and improvement in these factors can help explain these progressive trends in brain size and brain health. These trends might be a contributing factor in the decline of dementia cases among Framingham Heart study participants over the course of three decades, a trend that was highlighted in an earlier report. 

The study notes that differences in age-related brain atrophy should be analyzed using a longitudinal study model, which could provide support and strengthen the validity of trends associated with brain reserve, and that cross-sectional design has been a limitation in this regard.