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As individuals age, subtle decreases in brain size occur, a natural phenomenon observed in healthy aging. However, in individuals affected by dementia, the progressive damage to nerve cells leads to widespread brain atrophy, prompting questions about the relationship between brain size and dementia risk.

A study conducted by researchers at UC Davis Health, published in JAMA Neurology, suggests a potential correlation between brain size and dementia risk.

Analyzing data from the Framingham Heart Study, which tracked 15,000 individuals over 75 years, researchers observed a significant increase in brain size among individuals born in the 1970s compared to those born in the 1930s.

According to Charles DeCarli, MD, lead author of the study, larger brain structures, indicative of increased brain reserve, may mitigate the effects of age-related brain diseases such as Alzheimer's and related dementias.

However, while genetics play a significant role in brain size, external influences such as health, education, and lifestyle factors also contribute to brain development and long-term brain health.

"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," Ozama Ismail, PhD, Alzheimer's Association director of scientific programs, who was not involved in the study, told Medical News Today.

While previous studies have proposed the "brain reserve hypothesis," suggesting that larger brain volume offers protection against dementia pathology, experts emphasize the importance of cognitive reserve - the brain's ability to function effectively - in mitigating dementia risk.

Additionally, the study's predominantly non-Hispanic White, well-educated cohort highlights the need for more diverse research populations to draw comprehensive conclusions about brain health and dementia risk.

Looking ahead, ongoing studies such as the U.S. POINTER Study aim to address these gaps in research by including diverse populations and examining lifestyle interventions to reduce dementia risk.

"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," Ismael said.