ALB and depressive disorder: Building on prior epidemiological findings (4, 9), we aim to: (1) quantify independent associations between nocturia, depression severity, and cognitive dysfunction in at-risk populations; (2) characterize non-linear dose-response patterns using RCS, adjusted for demographic and behavioral confounders; (3) evaluate the mediating roles of serum Alb and hemoglobin in these associations; and (4) investigate sex- and age-stratified effect modifications.