Neutrophil-to-lymphocyte ratio is associated with short-term mortality in patients with acute respiratory distress syndrome: a meta-analysis

To investigate the association between neutrophil-to-lymphocyte ratio (NLR) and short-term mortality in patients with acute respiratory distress syndrome (ARDS) through a comprehensive meta-analysis of cohort studies. We performed a comprehensive literature search across Pubmed, Web of Science, and Embase from inception of the databases to July 31, 2025. To quantify the relationship between the NLR and short-term mortality in patients with ARDS, Hazard Ratios (HRs) were pooled using random or fixed-effects models based on heterogeneity (I2 statistic). Publication bias was evaluated using funnel plots and the trim-and-fill method. Sensitivity analyses and subgroup analyses were conducted to assess the stability and potential influences of study characteristics. Eight cohort studies involving 3396 participants were included. In studies treating NLR as a continuous variable, per-unit or standard deviation increase in NLR was associated with the higher risk of short-term mortality (HR = 2.25, 95% CI[confidence interval] 1.28–3.96, I2 = 92.1%). In studies categorizing NLR, higher NLR categories were associated with higher mortality (HR = 1.59, 95% CI 1.28–1.97, I2 = 60.0%). Funnel plot asymmetry suggested minor publication bias, which was corrected using the trim-and-fill method, yielding an adjusted HR of 1.91 (95% CI 1.01–3.60). Sensitivity analyses confirmed the robustness of these findings. Subgroup analyses showed that sample size, NOS score, and country of study significantly influenced the results. Meta-regression indicated that these factors collectively explained a substantial portion of the observed heterogeneity. This meta-analysis demonstrates that elevated NLR is associated with increased short-term mortality in ARDS patients. NLR may serve as a reliable prognostic marker. Future research should focus on validating these findings in diverse populations and exploring the underlying mechanisms.