Objectives: Recent studies suggested an association between delayed left ventricular (LV) relaxation and increased arterial stiffness and wave reflection. We aimed (i) to assess whether this association is already present in apparently healthy, middle-aged individuals and (ii) to determine to what extent this relationship is modulated by age and weight. Methods: 2524 subjects (1223 M) aged 35–56 years, free from overt cardiovascular disease were included in this study. LV relaxation was quantified by early diastolic tissue velocity (E’). Large artery stiffness was estimated by carotid–femoral pulse wave velocity (PWV) and the carotid distensibility coefficient (DC). Wave reflection was characterized by carotid augmentation index (AIx) and reflection magnitude (RM), Results: Strong bivariate correlations were observed between E’ and age (r = -0.506), DC (r = 0.393), PWV (r = -0.362), central systolic blood pressure (SBP, r = -0.331), weight (r = -0.314), RM (r = -0.156) and AIx (r = -0.142, all p<0.001). A multiple linear regression model revealed age as the primary independent determinant of E’, followed by weight. The remaining variables only contributed marginally to the model’s predictive accuracy (see table). Conclusions: Age, weight and arterial loading significantly determine early LV relaxation. Further analyses are needed to examine whether the statistical correlation between E’ and arterial loading is direct (mechanical) or indirect (through age and body size).