Direct and mediating effects of multilingualism on reducing perceived loneliness in the aging brain.

Amidst a rapidly aging global population, identifying life experience factors that sustain cognitive vitality and social resilience is a paramount scientific challenge. While multilingualism is frequently associated with the preservation of executive functions and the delayed onset of dementia, its potential benefits for social and emotional well-being remain underexplored. This study investigates the association between multilingualism and perceived loneliness, a critical determinant of health in older adults, and examines whether brain regions involved in social semantics mediate this link. We analyzed gray matter volume using structural magnetic resonance imaging in 197 cognitively healthy older adults possessing varying levels of multilingual experience, while accessing loneliness using the UCLA Loneliness Scale. Whole-brain and region-of-interest analyses revealed that greater multilingual experience is linked to increased gray matter volume in the left anterior temporal lobe (ATL). This region is central to semantic and social conceptual processing. Crucially, ATL volume significantly mediated the relationship between multilingualism and loneliness, suggesting a specific neural pathway connecting language experience to mental health. These findings broaden existing cognitive reserve frameworks by demonstrating that the protective effects of multilingualism extend beyond executive control to encompass the mechanisms underlying social cognition. By enriching conceptual and interpersonal representations, multilingualism likely facilitates meaningful social engagement and mitigates loneliness. This study provides neuroimaging evidence that multilingualism benefits cognitive reserve, mental health, and brain aging, highlighting the necessity of integrating social and cognitive pathways into neurocognitive aging frameworks.