Correlation of red cell distribution width with depression among adults with and without self-reported history of cancer

Red blood cell distribution width (RDW), recognized as a biomarker for systemic inflammation and oxidative stress, has been associated with various health outcomes, including depression. However, the precise relationship between RDW and depression, particularly in individuals with differing cancer statuses, remains ambiguous. In this cross-sectional study, data from 32,467 adults aged 18 and older from the NHANES 2005-2018 cohort were analyzed. Depressive symptoms were evaluated using the Patient Health Questionnaire-9 (PHQ-9), where a score of 10 or above indicated moderate-to-severe depression. Multivariate logistic regression models assessed the association between RDW and depression, accounting for demographic, lifestyle, clinical, and laboratory covariates. Subgroup analyses considered cancer status, revealing that a higher RDW was associated with depression in the general population [adjusted odds ratio (OR), 1.04; 95% confidence interval (CI), 1.01-1.07]. This link persisted for individuals without cancer (adjusted OR, 1.05; 95% CI, 1.02-1.08) but not for those with self-reported cancer history (adjusted OR, 0.97; 95% CI, 0.89-1.06), indicating significant interaction differences (P for interaction = 0.012). These results suggest RDW may serve as a cost-effective marker associated with depression, particularly in individuals without cancer, and highlight the need for further exploration of its implications and mechanisms across various clinical contexts.