Association between RAR and the prevalence and prognosis of suicidal ideation: evidence from a large population-based study

Previous studies have suggested that the red blood cell distribution width to albumin ratio (RAR), a novel inflammatory biomarker, may better predict adverse outcomes in patients with various diseases. Chronic inflammation has been linked to an increased prevalence of suicidal ideation. The weight-adjusted-waist index (WWI), a recently developed anthropometric measure, provides a more accurate assessment of obesity, which is itself a risk factor for suicidal ideation. This study aimed to investigate the association between RAR and suicidal ideation, and to assess whether WWI mediates this relationship. Data from 30,911 participants in the 2005–2018 National Health and Nutrition Examination Survey (NHANES) were analyzed. Multivariable logistic regression, restricted cubic spline (RCS) analysis, and subgroup analyses were performed to examine the association between RAR and suicidal ideation. Mediation analysis was used to evaluate the potential mediating role of WWI. Additionally, Cox proportional hazards models were applied to assess the associations of RAR with cardiovascular and all-cause mortality among participants with suicidal ideation. In the cross-sectional analysis, 1,172 participants (3.8%) reported suicidal ideation. Weighted multivariable logistic regression revealed an independent association between RAR and suicidal ideation (OR = 1.39, 95% CI: 1.19–1.62, P < 0.001). Similar results were observed for WWI. RCS analysis indicated a significant linear positive relationship between RAR and suicidal ideation. Mediation analysis showed that WWI accounted for 19.00% of the association. In the cohort analysis, there were 153 all-cause deaths (13%) and 33 cardiovascular deaths (2.8%) among participants with suicidal ideation. Weighted multivariable Cox regression demonstrated that higher RAR was associated with increased risks of all-cause mortality (HR = 2.08, 95% CI: 1.48–2.92, P < 0.001) and cardiovascular mortality (HR = 2.22, 95% CI: 1.14–4.32, P = 0.019). RAR was positively associated with both the prevalence of suicidal ideation and mortality among individuals with suicidal ideation. Although this study provides valuable insights into the potential role of RAR in suicidal health, its cross-sectional design limits the ability to infer causality. Future longitudinal studies are warranted to confirm these findings and further elucidate the underlying mechanisms.