Abstract
BACKGROUND: Systemic inflammation and immune dysregulation may be associated with asthma onset and progression. Neutrophil percentage-to-albumin ratio (NPAR) is a novel marker of systemic inflammation. We aimed to investigate the association of NPAR with all-cause and respiratory disease-related mortality in adults with asthma. METHODS: This is a retrospective cohort study using data from 5032 participants with asthma from the National Health and Nutrition (NHANES) spanning from 1999 to 2018. NPAR was calculated by neutrophil percentage (% of total white blood cell count) × 100/serum albumin (g/dl). Asthma was self-reported based on responses to a standardized questionnaire in NHANES. Mortality data were obtained through retrospective matching with the National Death Index (NDI), using secondary data from NHANES. Survey-weighted multivariable Cox proportional hazards regression analysis was used to explore these associations. RESULTS: After a median follow-up duration of 104 months, 696 participants died, of which 101 were respiratory disease-related deaths. In fully adjusted models, NPAR was significantly and positively associated with both all-cause and respiratory disease-related mortality (hazard ratios [HR] of 1.13 and 1.25, respectively, both p < 0.0001). Compared to Q1, NPAR at Q4 was associated with significantly increased all-cause and respiratory disease-related mortality (all-cause: HR 2.23, p < 0.0001; respiratory disease-related: HR 3.55, p = 0.004). NPAR was nonlinearly associated with all-cause mortality, with an inflection point of 13.76. This association was significant only after the inflection point (HR 1.18, p < 0.0001). The effect of NPAR on all-cause mortality was more pronounced in those < 60 years of age (HR 1.19, p < 0.0001). CONCLUSIONS: Higher NPAR was associated with increased all-cause and respiratory disease-related mortality in US adults with asthma. Further exploration of the prognostic potential and underlying mechanisms of NPAR is needed. CLINICAL TRIAL NUMBER: Not applicable.