Monocyte-to-Albumin Ratio (MAR) Is Associated With All-Cause Mortality in Adult Stroke Patients: Evidence From NHANES (1999-2018).

OBJECTIVE

To investigate the association between the monocyte-to-albumin ratio (MAR) and all-cause mortality risk in stroke patients.

METHODS

We analyzed data from 2022 stroke participants (aged ≥ 20 years) in the National Health and Nutrition Examination Survey (NHANES) 1999-2018. MAR was calculated as the monocyte count (×109/L) divided by serum albumin (g/L). The outcome was all-cause mortality of stroke population. Multivariable Cox proportional hazards models were used to examine the association between MAR and all-cause mortality, with restricted cubic splines assessing dose-response relationships and Kaplan-Meier curves with log-rank tests evaluating cumulative survival probabilities. Furthermore, we compared the incremental predictive value of MAR against a conventional risk model (incorporating demographics and comorbidities) using the area under the curve (AUC), integrated discrimination improvement (IDI), and net reclassification improvement (NRI). Subgroup analyses and sensitivity analyses were performed, stratified by demographic and clinical characteristics, to verify robustness.

RESULTS

A total of 2022 participants were included, of whom 1016 (50.2%) were male and 1506 (74.5%) were aged ≥ 60 years. In multivariable Cox regression adjusting for demographic, lifestyle, and clinical covariates, elevated MAR was independently associated with all-cause mortality (per 1-unit increase: HR = 1.35, 95% CI: 1.21-1.50; T3 vs. T1: HR = 1.32, 95% CI: 1.12-1.55; both p < 0.05). Restricted cubic spline analysis revealed a nonlinear dose-response relationship (p for nonlinearity = 0.001). Kaplan-Meier curves demonstrated lower survival probabilities in the highest MAR tertile (T3) compared to the lowest (T1) (log-rank p < 0.001). With respect to model performance, incorporating MAR into the conventional risk model resulted in a statistically significant but modest improvement in discrimination (Δ A U C = 0.0158) and reclassification accuracy (IDI = 0.0129, NRI = 0.208; all p < 0.05). Subgroup and sensitivity analyses confirmed the robustness of this association across various strata.

CONCLUSION

Elevated MAR is independently associated with long-term mortality in stroke survivors, reflecting underlying inflammation and nutritional insufficiency. These findings support MAR's potential utility as a research tool in prospective cohort studies.