Social disconnection and cognitive aging across the life course: coordinated longitudinal analysis of three national cohort studies

This study aims to better understand the effect of social disconnection on cognitive aging regarding its life course variation, temporal dynamics, and multidimensionality.We conducted coordinated data analysis of three large U.S. population-based longitudinal cohort panels (Add Health I–VI, MIDUS 1–3, and HRS 2006–2020) consisting of 18,553 individuals aged 11+. We harmonized measures of longitudinal patterns of social isolation and loneliness (never/transient/persistent), episodic memory (word recalls), and working memory (backward digit span and serial 7’s) across datasets. We estimated growth curve models to assess prospective associations of social isolation and loneliness with subsequent memory trajectories from adolescence to old adulthood.We found strong detrimental effects of social isolation in both young and older adulthood and loneliness in older adulthood on memory function. Longer (particularly persistent) exposures to isolation and loneliness predicted poorer memory test scores. These effects were attenuated but largely remained significant after adjusting for sociodemographic, behavioral, and health risk factors. Social isolation and loneliness show weaker and less consistent associations with the rate of memory decline across the life course samples.Comparative life course research helped to elucidate the complex relationship between social disconnection and memory change and inform the timing and duration of cognitive impacts of objective and subjective social disconnection. Interventions to promote healthy aging should focus on reducing the chronicity of isolation starting early in life and feelings of loneliness in later life. Future research should include additional longitudinal data to further investigate links between cognition, social disconnection, and underlying mechanisms.