Blood Neutrophil Count is Associated with Body Mass Index in Adolescents with Asthma.

Background: Sputum neutrophils are associated with severe asthma, poor pulmonary function and high body mass index (BMI) in adult patients. However, little is known about the relationships between blood neutrophils, BMI and asthma severity in pediatric patients. This brief report is to assess the predictive value of blood neutrophils for asthma severity, BMI and pulmonary function in adolescents with asthma.

Methods: The study included 166 adolescents with physician diagnosed asthma for at least 1 year. Participants were recruited from three metropolitan cities in the U.S. BMI-for-age percentile (BMI %) was determined by standardized charts and absolute neutrophil counts (cells/μL) were obtained from the complete blood count. Asthma severity was measured based on the national guidelines. Spirometry was performed to obtain percent predicted values for Forced Expiratory Volume in 1 second (FEV1), Forced Vital Capacity (FVC), and FEV1/FVC ratio as markers for pulmonary function.

Results: The average age of participants was 14.79 years (± 1.86) and 54% were female. The majority (84%) were black. Fifty-five percent of the sample were either overweight (21%) or obese (34%). Blood neutrophil count was significantly correlated with BMI% (r=0.25, p=.001), but not with symptom severity (r=0.087, p=.268), FEV1 (r=-0.00, p=.937), or FVC (r=-0.010, p=.897).After controlling for sex, age, and age at asthma diagnosis, blood neutrophil count was a significant predictor for overweightness or obesity (OR=1.38, 95% CI 1.11, 1.75, p=0.01).

Conclusions: Elevated blood neutrophils are associated with higher BMI, but not lung function or symptom severity in our adolescent sample with asthma. This study suggests blood neutrophils may be a potential inflammatory biomarker for overweightness and obesity in adolescents with asthma, but not for asthma morbidity.