Low gestational vitamin D level and childhood asthma are related to impaired lung function in high-risk children

Background Lung function impairment in early life often persists into adulthood. Therefore, identifying risk factors for low childhood lung function is crucial. Objective We examined the effect of 25-hydroxyvitamin D (25[OH]D) level and childhood asthma phenotype on childhood lung function in the Vitamin D Antenatal Asthma Reduction Trial (VDAART). Methods The 25(OH)D level was measured at set time points in mothers during pregnancy and in children during early life. On the basis of parental reports, children were categorized into 3 clinical phenotypes: asymptomatic/infrequent wheeze, early transient wheeze, and asthma at age 6 years. Lung function was assessed with impulse oscillometry at ages 4, 5, and 6 years and with spirometry at ages 5 and 6 years. Results A total of 570 mother-child pairs were included in this post hoc analysis. Mean gestational 25(OH)D-level quartiles were negatively associated with child respiratory resistance at 5 Hz (R5) from age 4 to 6 years (β, −0.021 kPa/L/s; 95% CI, −0.035 to −0.007; P = .003) and positively associated with FEV1 (β, 0.018 L; 95% CI, 0.005-0.031; P = .008) and forced vital capacity (β, 0.022 L; 95% CI, 0.009-0.036; P = .002) from age 5 to 6 years. Children with asthma at age 6 years had lower lung function from age 4 to 6 years than the asymptomatic/infrequent wheeze group (β, 0.065 kPa/L/s; 95% CI, 0.028 to 0.102; P < .001 for R5 and β, −0.063 L; 95% CI, −0.099 to −0.028; P < .001 for FEV1). Conclusions Low gestational 25(OH)D level and childhood asthma are important risk factors for decreased lung function in early childhood.