Larger brain size may indicate lower dementia risk

Previous studiesTrusted Source have suggested that larger brain volume protects against the effects of dementia pathology, arguing that those with a greater head circumference can endure a greater degree of damage before they start to show cognitive impairment.

This ‘brain reserve hypothesis’Trusted Source suggests that a larger brain volume, with more neurons and synaptic connections, could provide protection against cognitive decline from brain atrophy. Experts use ICV on MRI and head circumference as indicators of brain volume.

However, this observed effect could be due to other factors, as Ismail told Medical News Today:

“Larger brain volumes may be beneficial in maintaining resilience to cognitive decline and dementia, but many other factors can contribute to resilience, including genetics, environment, socioeconomic status, education, and active vs. sedentary lifestyle.”

Other studiesTrusted Source have stressed that cognitive reserve — how well the brain functions — is more important than actual brain size in relation to dementia risk. People with a higher cognitive reserve tend to show dementia symptoms later, but then decline faster once symptoms become evident.

The researchers in this study suggest that the increase in brain volumes over the four birth decades in their study could predict a lower risk of dementia in people born later in the FHS.

Call for more diverse studies

The researchers acknowledge that their study cohort was predominantly non-Hispanic White, healthy, and well-educated, so not representative of the general population of the United States. However, they emphasize that the strengths of the study include the fact that it has followed 3 generations, spanning more than 80 years of births.

Ismail called for further studies that include a greater diversity of people:

“More diversity in research populations is needed before conclusions can be made about changes in brain size over generations and the influence it may have on cognition, resilience, and dementia risk.”

“This is particularly important given the known sociocultural and health disparities that exist in underrepresented populations,” he added.

The Alzheimer’s Association’s U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk (U.S. POINTER), which should publish results next year, aims to help address this gap in the research, as Ismail told MNT:

“In the U.S. POINTER Study, more than 2,000 volunteer older adults who are at increased risk for cognitive decline are enrolled and will be followed for two years. Nearly 30% of current participants are from populations historically underrepresented in Alzheimer’s/dementia research.”