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

Abstract

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.

Keywords: VDAART; Vitamin D; childhood asthma; impulse oscillometry; lung function; spirometry; tobacco smoke.