Investigation of brain volume changes associated with aging: Results from the fourth research on osteoarthritis/osteoporosis against disability survey.

Aim: This study aims to investigate the impact of aging on brain volume among community residents in Japan, focusing on trends over time and specific brain structures.

Methods: We analyzed data from the fourth survey (2015-2016) of the Research on Osteoarthritis/Osteoporosis Against Disability project, encompassing 2146 community residents from Japan's mountainous and coastal regions. A total of 1755 participants (81.8% of the baseline population) underwent extensive data collection including lifestyle and health questionnaires, anthropometric measurements and brain magnetic resonance imaging. The imaging data were processed to examine correlations between total brain volume, gray matter volume (GMV), white matter volume (WMV), cerebrospinal fluid volume and participant age.

Results: Analysis showed significant sex differences in total brain volume, with GMV demonstrating a strong negative correlation with age - more pronounced than the moderate negative correlation seen in WMV. Cerebrospinal fluid volume exhibited a strong positive correlation with age. Notably, specific brain regions such as the bilateral amygdala, hippocampus, thalamus and primary motor cortex showed significant age-related volume reductions.

Conclusion: This study confirms that GMV and WMV are smaller in older individuals in the Japanese population, with more pronounced differences in GMV. The amygdala, hippocampus, thalamus and primary motor cortex were particularly affected. Geriatr Gerontol Int 2025; ••: ••-••.