Brain volume and dementia risk

Although the overall prevalence of dementia has been increasing along with population growth, the incidence of dementia, the number of new cases per year, has actually been decreasing in many parts of the world. Suggested causes of this decrease in dementia have included greater educational achievement and better management of cardiovascular risk factors such as hypertension, hyperlipidemia, diabetes and smoking. A recent study reported in JAMA Neurology using MRI data collected for the ongoing Framingham Study suggests that this decrease in dementia incidence may be related to larger brain volumes as early as childhood. As seen in the figure below, total intracranial volume, hippocampus volume, white matter volume, and most impressively brain cortical surface area increased as a function of birth decade. Conversely, the brain cortical thickness was smaller in subjects born more recently.  The authors suggest that this represents a thinning of the cerebral cortex to accommodate the enlarging brain. They propose that these increases in brain volume may reflect “improvements in early life environmental influences through health, social-cultural, and educational factors, as well as improvements in modifiable risk factors leading to better brain health and reserve. While these effects are likely to be small at the level of the individual, they are likely to be substantial at the population level, adding to growing literature that suggests optimized brain development and ideal health through modification of risk factors could substantially modify the effect of common neurodegenerative diseases such as stroke and Alzheimer disease on dementia incidence.” Cognitive resilience appears to be on the rise!