Social isolation and cognitive functioning trajectories from midlife to later life in four high- and middle-income countries.

The relationship between social connections and cognitive health is well-established, yet its implications vary significantly across life stages and sociocultural contexts. This study provides new insights by using Gateway to Global Aging Data (2010-18) to examine cognitive functioning trajectories from mid- to later life across four high- and middle-income countries: the United States, England, China and Mexico. We consider overall social isolation as well as its specific dimensions, including partnership status, contact with children and friends, and social participation. Using growth curve models, we assess both levels of cognitive functioning and the rate of cognitive change with age. Results show that socially isolated adults consistently exhibit lower cognitive functioning than their non-isolated counterparts in all countries except England, with gaps more pronounced in China and Mexico than in the United States. Cross-national differences also emerge across dimensions of isolation. For instance, not having a partner significantly predicts lower cognition in China and the United States but not in England or Mexico. Contact with children plays a critical role in China and Mexico and becomes more salient in later life in the United States. Beyond family ties, maintaining friendships and engaging in social activities support cognitive health across most settings and become increasingly important with age. These findings demonstrate that the cognitive consequences of social isolation depend not only on who is isolated, but also on when isolation occurs and how it aligns with broader social contexts and life course dynamics.