Adult Socioeconomic Position Mediates the Association Between Childhood Socioeconomic Position and Later-Life Frailty Trajectory: A Nationally Representative Cohort Study.

Background and objectives: Early-life risk factors influence the aging process in the short term and shape its trajectory in the long term. We aim to (1) explore the association between childhood socioeconomic position (cSEP) and frailty trajectories and (2) test whether adult socioeconomic position (aSEP) mediates the association between cSEP and frailty trajectories.

Research design and methods: We analyzed 4 waves of the China Health and Retirement Longitudinal Study data. The frailty index was estimated based on the number of individual deficits across 40 indicator variables. Principal component analysis was used to generate cSEP and aSEP. Group-based trajectory models were used to identify the patterns of frailty trajectories over time. Causal mediation analysis was conducted to determine whether the aSEP mediated the association between cSEP and frailty trajectories.

Results: We identified 3 distinct trajectories of frailty progression. Low cSEP was significantly associated with "High and increasing frailty trajectory" (odds ratio [OR] = 1.76, 95% confidence intervals [95% CI]: 1.38-2.23; adjusted OR = 1.55, 95% CI: 1.22-1.97). About 30% of the cSEP effect on rising frailty trajectory was mediated through the aSEP, and there is a significant gender disparity in the mediating effect of aSEP (18% among men and 51% among women, respectively).

Discussion and implications: Our findings suggest that policies that initially benefit children will yield well-being benefits as they reach adulthood. Promoting ongoing cSEP advantages increases the likelihood of delaying frailty progression in later life. This study underscores the critical importance of addressing social determinants of health throughout one's life course to foster healthy aging and diminish health disparities in later stages of life.