Phenotypic age acceleration through a lens of intersectional inequalities in the German national cohort (NAKO)

BackgroundDifferences in biological aging have been linked to sociodemographic characteristics, but how multiple social inequalities intersect to shape biological aging differences across population subgroups remains unclear. By integrating a perspective of biology of aging with intersectionality theory, we aimed to investigate the joint influence of multiple social determinants on phenotypic age acceleration (i.e., difference between biological and chronological age). MethodsWe analysed data from 173,925 participants in the German NAKO study to calculate phenotypic age acceleration. We then created intersectional social strata based on individual sociodemographic characteristics to assess differences in phenotypic age acceleration through an intersectional Multilevel Analysis of Individual Heterogeneity and Discriminatory Accuracy (MAIHDA). ResultsAll intersectional strata displayed phenotypic age deceleration (i.e., were biologically younger than their chronological age). This advantage was weakest among men without a migration background, living alone and with low socioeconomic status. Substantial discriminatory accuracy of the strata (7.13%) implied intersectional inequalities. Most differences were driven by additive effects, with modest multiplicative effects due to intersectional interactions. We found multiplicative effects representing increased risk for individuals with migration background, not living alone and with medium/high socioeconomic status, or those without migration background, living alone and with medium/low socioeconomic status. ConclusionOur study provides novel insights on the intersectional stratification of biological aging, highlighting the significance of bio x social interactions for the aging process. Future epidemiological studies should focus on the mechanisms linking multiple social inequalities and accelerated biological aging, using intersectionally-informed targeted interventions that address both social and aging-related inequalities. WHAT IS ALREADY KNOWN ON THIS TOPICO_LIBiological aging varies by sociodemographic factors, with lower socioeconomic status linked to accelerated aging. However, most studies examined single social determinants rather than the interaction effects at their intersections. C_LI WHAT THIS STUDY ADDSO_LIUsing the innovative MAIHDA framework, we identify intersectional disparities in biological aging in a large German cohort. C_LIO_LIWhile aging differences are largely additive, certain social strata experience amplified disparities due to intersectional effects. C_LI HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE AND/OR POLICYO_LIOur findings support targeted public health strategies addressing cumulative social disadvantages in aging. C_LIO_LIFuture research should integrate intersectional approaches to better understand aging inequalities and design tailored interventions. C_LI