Wheezing in Black Preterm Infants: Impact of Vitamin D Supplementation Strategy

Black infants face the highest rates of prematurity in the U.S. (18%), have high rates of prematurity-associated wheezing illnesses, and tend to have lower vitamin D levels. The goal of this \[comparative effectiveness\] study is to identify a vit. D supplementation strategy that minimizes recurrent wheezing in infancy. Long recognized as important for bone health, a growing body of evidence suggests that vit. D may play a role in the regulation and development of many organ systems. The D pathway regulates lung inflammation and impacts morphogenesis, structure, and cell growth and survival in bronchial smooth muscle. Vit. D exposure has the potential to skew cytokine expression from a Th1 (less allergic) to a Th2 (more allergic) phenotype. Due to their developmental immaturity, preterm infants may be particularly vulnerable to any positive or negative effects of vit. D supplementation on the lung, airway, and immune system. Our preliminary data, supported by the literature, suggests that overly aggressive vit. D supplementation may inadvertently increase wheezing in infancy in black, but not white, preterm infants; however, vit. D deficiency could theoretically also increase wheezing via vulnerability to respiratory pathogens. The proposed study is a randomized clinical trial comparing the effect of two different enteral vitamin D supplementation strategies on recurrent wheezing in infancy in 300 black infants born preterm at 28 0/7-36 6/7 wks gestational age, a population for whom neither vit. D requirements nor optimal vit. D serum levels have been established. The investigators will test two strategies: (I) sustained supplementation until 6 mo. of age adjusted for prematurity, and (II) cessation of supplementation when a minimum dietary intake of 200 IU/day is reached. The specific aims are to characterize the effect of each strategy on (aim 1) recurrent wheezing and (aim 2) allergic sensitization and atopy. The investigators will (aim 3) explore the relationship between vit. D serum levels and recurrent wheezing. The investigators hypothesize that strategy II will be more effective in promoting pulmonary health by minimizing recurrent wheezing, allergic sensitization, and overall healthcare utilization, and will be sufficient to prevent clinical vit. D deficiency. The investigators also hypothesize that optimal vit. D serum levels will be lower than the norms for other populations.