Vitamin D and pulmonary function in obese asthmatic children

Area of Science:

• Pediatric Pulmonology
• Nutritional Science
• Immunology

Background:

• Asthma exacerbations and related morbidity are more prevalent in children with co-existing vitamin D deficiency and obesity.
• Minority children are disproportionately affected by these co-morbidities.
• The impact of combined vitamin D deficiency and obesity on lung function in pediatric asthma is not well understood.

Purpose of the Study:

• To investigate the association between vitamin D status and pulmonary function in obese and normal-weight children with asthma.
• To explore the role of systemic inflammation (Th1 and Th2 cytokines) in this relationship.

Main Methods:

• A cohort of 72 obese and 71 normal-weight Hispanic and African-American children with asthma was studied.
• Pulmonary function was assessed using percent-predicted values.
• Serum 25-hydroxyvitamin D (25-OHD) levels were categorized as sufficient (≥30 ng/ml), insufficient (<30 and ≥20 ng/ml), or deficient (<20 ng/ml).
• Serum cytokines were quantified, and regression analysis was used to examine the role of inflammation.

Main Results:

• Vitamin D deficiency was found in 50% of the children, with no difference between obese and normal-weight groups.
• Obese children with vitamin D deficiency exhibited significantly lower Forced Expiratory Volume in the first second and Functional Residual Capacity compared to sufficient counterparts.
• Total Lung Capacity was also lower in vitamin D deficient obese asthmatics compared to insufficient counterparts.
• No significant associations were observed in normal-weight asthmatics or influenced by systemic inflammation.

Conclusions:

• Vitamin D deficiency is associated with reduced pulmonary function in obese children with asthma.
• This association is independent of Th1 and Th2 inflammatory markers.
• Vitamin D deficiency may be a contributing factor to the obese-asthma phenotype.