Lymphocyte level is a potential biomarker for the neonatal apnea risk and the length of intensive care unit stay in neonates.

This study aimed to investigate the association of lymphocyte levels with the risk of neonatal apnea and the length of intensive care unit (ICU) stay in neonates. The data on neonates were derived from the MIMIC III database. Baseline characteristics and laboratory parameters were compared between the apnea and no-apnea groups. Logistic regression models were used to assess the association between lymphocyte levels and apnea risk. Generalized linear models (GLM) were performed to explore the relationship between lymphocyte levels and ICU stay. Moreover, latent class trajectory models (LCTM) evaluated lymphocyte trajectory changes over time, with subgroup analysis based on treatment types and gestational age. A total of 3408 neonates were finally included: 1121 with apnea and 2287 without apnea. Higher lymphocyte levels were significantly associated with an increased risk of apnea and a shorter ICU stay among neonates with apnea. LCTM identified four lymphocyte trajectory groups: persistently low, low-rise, moderate-rise, and high-rise. Trajectory groups showed no significant association with length of ICU stay. However, among the neonates treated with vancomycin or acetaminophen subgroups, the high-rise trajectory and moderate-rise trajectory had significantly shorter ICU stays compared to persistently low trajectory. In conclusion, elevated lymphocyte levels are associated with a higher risk of neonatal apnea and a shorter ICU stay. Specific treatment types may modulate the association of lymphocyte trajectory with ICU stay duration, suggesting potential for targeted intervention.