Association of Serum Albumin With Apnea in Infants With Bronchiolitis: A Secondary Analysis of Data From the MARC-35 Study

IMPORTANCE: Apnea is a rare, life-threatening complication of bronchiolitis, the leading cause of infant hospitalization in the United States. Currently, no objective method exists for identifying which infants will become apneic. OBJECTIVE: To investigate whether serum albumin levels are associated with apnea in infants with severe bronchiolitis. DESIGN, SETTING, AND PARTICIPANTS: A secondary data analysis of the 35th Multicenter Airway Research Collaboration, an ongoing multicenter cohort study of infants hospitalized for bronchiolitis, was conducted from December 11, 2018, to May 30, 2019. Seventeen hospitals across the United States enrolled infants (n = 1016) during 3 consecutive bronchiolitis seasons (November 1 to April 30) between 2011 and 2014. Infants with heart-lung disease or a gestational age less than 32 weeks were excluded. EXPOSURES: Serum albumin level was categorized as low (<3.8 g/dL) or normal (≥3.8 g/dL). MAIN OUTCOMES AND MEASURES: Apnea during the hospitalization. RESULTS: Of the 1016 infants hospitalized for bronchiolitis, the median (interquartile range [IQR]) age was 3 (2-6) months, 610 (60.0%) were male, and 186 (18.3%) were born preterm (32-37 weeks’ gestation). Among the 25 infants (2.5%) with apnea while hospitalized, the median (IQR) serum albumin level was 3.5 (3.1-3.6) g/dL, and 22 (88.0%) had low serum albumin levels. The prevalence of apnea was 5.7% among all infants with low albumin levels, compared with 0.5% prevalence in infants with normal serum albumin levels. In unadjusted analyses, apnea was associated with younger age, preterm birth, weight-for-age z score, and low albumin (odds ratio [OR], 12.69; 95% CI, 3.23-49.82). After adjustment for age, preterm birth, and weight-for-age z score, low serum albumin levels remained statistically significantly associated with apnea (OR, 4.42; 95% CI, 1.21-16.18). CONCLUSIONS AND RELEVANCE: Low serum albumin levels appeared to be associated with increased risk of apnea after adjustment for known apnea risk factors. This finding provides a path to potentially identifying apnea, a life-threatening complication of bronchiolitis.