Lower oxidative balance score and higher systemic immune-inflammatory indices are associated with current asthma

Whether the oxidative balance score (OBS) and complete blood count (CBC)-derived inflammatory indices are associated with current asthma, relative to a correctly defined never-asthma comparison group and accounting for the survey's complex sampling design, has not been investigated. This cross-sectional study used data from a nationally representative health survey cycle (August 2021-August 2023). Current asthma (n = 517) and never-asthma (n = 3725) groups were defined using validated lifetime-diagnosis and current-status questions; a former-asthma group (n = 308) was analyzed descriptively. Six CBC-derived indices (neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, systemic immune-inflammation index, systemic inflammatory response index, eosinophil-to-lymphocyte ratio, and monocyte-to-lymphocyte ratio) were calculated from absolute blood counts. Survey-weighted logistic regression, incorporating NHANES sampling weights, stratification, and primary sampling units, estimated odds ratios (ORs) for current asthma per 1-standard deviation increase in OBS and each index, with exposure-specific covariate adjustment and Benjamini-Hochberg false discovery rate correction across the 6-index panel. Current-asthma participants had lower OBS (18.7 ± 6.9 vs 20.4 ± 6.9) than never-asthma participants and numerically higher values across all 6 inflammatory indices and high-sensitivity C-reactive protein (hsCRP), reaching unadjusted significance for OBS, systemic immune-inflammation index, eosinophil-to-lymphocyte ratio, and hsCRP. In survey-weighted models, OBS remained associated with lower odds of current asthma (OR 0.77, 95% confidence interval 0.68-0.87), and all 6 inflammatory indices remained associated with higher odds (ORs 1.12-1.32), surviving FDR correction (all q < .05). The OBS association was consistent in a 2-day dietary sensitivity analysis, while inflammatory-index estimates were materially unchanged after additional adjustment for race/ethnicity. hsCRP was not associated with asthma status after adjustment. Within the current-asthma group, OBS was not associated with CBC-derived inflammatory indices, although hsCRP differed across OBS quartiles in a secondary analysis (FDR q = .041). Lower OBS and higher levels of several CBC-derived inflammatory indices were each associated with current asthma compared with never-asthma status; however, OBS was not associated with inflammatory index levels within the current-asthma group. These cross-sectional associations do not establish causality but support prospective investigation of dietary and lifestyle antioxidant status and systemic inflammatory indices as correlates of asthma.