Relationship stress and epigenetic age acceleration among older U.S. adults in the Midlife in the United States study

<h4>Background</h4>Chronic interpersonal stress has been linked to accelerated biological aging, but questions remain about which relationship stress domains may be most consequential during midlife.<h4>Research design and methods</h4>Linear regression models quantified the cross-sectional associations between domain-specific relationship stressors (marital risk, partner strain, family strain, friendship strain) and next-generation epigenetic clocks (DunedinPACE and GrimAge2) in 1,310 midlife adults from the Midlife in the United States study (mean age = 51, SD = 13).<h4>Results</h4>Controlling for sociodemographic and health behaviors, we found that friendship strain was uniquely associated with accelerated aging (GrimAge2: 0.03 SD increase, 95% CI: 0.01, 0.05, <i>p</i> = 0.003; DunedinPACE: 0.05 SD increase, 95% CI: 0.01, 0.09, <i>p</i> = 0.030). No statistically significant associations were observed for the other stressors with GrimAge2 or DunedinPACE in fully adjusted models.<h4>Conclusions</h4>These findings identify friendship strain as a potential specific risk factor for accelerated biological aging in midlife. Future research should investigate behavioral and physiological mechanisms linking friendship quality to cellular aging.