Association of Relative Fat Mass with Incident Depressive Symptoms among Older Adults: A 14-Year Analysis of the ELSA and HRS Cohorts

ObjectiveNot known is whether relative fat mass (RFM)-a height- and waist-based estimator of total adiposity-predicts late-life depressive symptoms better than conventional anthropometrics.MethodsThis study analyzed harmonized data from two nationally representative aging cohorts: the English Longitudinal Study of Ageing (ELSA) and the US Health and Retirement Study (HRS). Adults ≥50 years without baseline depressive symptoms (CES-D-8 <3) and with valid anthropometrics and covariates were followed biennially for up to 14 years (ELSA n = 4176; HRS n = 5054). RFM was computed from measured height and waist circumference and examined continuously (each 1-standard deviation SD increase) and by tertiles. Incident depressive symptoms were defined as CES-D-8 ≥3 at follow-up. Cox models estimated hazard ratios (HR) with progressive adjustment. Dose-response was assessed using restricted cubic splines. Predictive performance was compared with body mass index (BMI) and waist circumference (WC) via time-dependent AUCs. Sensitivity analyses used multiple imputation and propensity-score matching.ResultsOver a mean of 8.60 years (ELSA) and 8.57 years (HRS), 1467 and 1769 participants developed incident depressive symptoms. Higher baseline RFM predicted incident depressive symptoms in both cohorts (for each 1-SD, Model 3: ELSA HR = 1.15, 95% CI = 1.06-1.25; HRS HR = 1.10, 95% CI = 1.05-1.16). Compared with low RFM, high RFM remained associated with higher risk (ELSA HR = 1.37, 95% CI = 1.12-1.67; HRS HR = 1.29, 95% CI = 1.14-1.46). Restricted cubic splines suggested a J-shaped association. Time-dependent AUCs showed RFM consistently outperformed BMI and WC across follow-up. Findings were robust in multiple imputation and propensity-matched analyses.ConclusionsIn two national cohorts of older adults, higher RFM was prospectively associated with incident depressive symptoms and demonstrated superior time-varying discrimination compared with BMI and WC, supporting RFM as a pragmatic tool for late-life depressive symptoms risk stratification.