Social relationships and immune aging in early midlife: Evidence from the National Longitudinal Study of Adolescent to Adult Health.

Aging of the immune system is characterized by changes in the T-cell compartment, including a decrease in naïve T-cells and an increase in memory T-cells. Stress exposures are known to predict accelerated immune aging in older adults. However, social relationships, which are often linked to stress mechanisms, have not been widely studied in relation to these adaptive immune biomarkers, particularly in younger populations. We examined associations between social relationships, in terms of quantity (Social Network Index, Close Contacts Index) and quality of relationships (spouse/partner, friends, and family members), and immune aging in a U.S-representative early midlife population (age 33-44) from Wave V of the National Longitudinal Study of Adolescent to Adult Health (n = 4451). DNA methylation data of venous blood samples collected during Wave V were used to compute CD4 memory:naïve, CD8 memory:naïve, and total CD8+:CD4+ T cell ratios; higher values indicate a more aged immune profile. Results from survey-weighted linear regression models adjusted for age, sex, race/ethnicity, and education indicated higher number of close friends and frequency of contact, alongside higher quality relationships with family members were associated with decreases in CD4 memory:naive ratios. The results for CD8 memory:naïve and CD8+:CD4+ ratios were mostly non-significant. Our findings suggest that higher quantity and quality of social relationships may help protect against immune aging, particularly in the CD4 T cell compartment, prior to midlife. This underscores the importance of interventions that enhance social relationships throughout life to promote healthy longevity.