Preterm birth reduces the incidence of atopy in adulthood

Background: Immunologic pathways are primed in early life. Preterm birth can influence this process and thereby affect whether a person will have atopy later in life. Previous studies on the effects of preterm birth on atopy in adulthood have been inconclusive and limited to children or subjects born moderately preterm. Objective: Our aim was to compare the incidence of atopy among young adults who were born preterm and at very low birth weight (<= 1500 g) with that of term-born young adults (control subjects). Methods: The study comprised 166 adults who were born preterm and at very low birth weight and 172 control subjects, all of whom were from the Helsinki Study of Very Low Birth Weight Adults. We assessed atopic predisposition at ages 18 to 27 years using skin prick tests for 6 common aeroallergens and measurements of serum concentrations of total IgE and 3 types of allergen-specific (cat, birch, and timothy) IgE. We asked the subjects whether they had been given a diagnosis of asthma or allergic rhinitis or had atopic eczema and analyzed data by using logistic or linear regression, adjusting for potential confounding factors. Results: The risk for having at least 1 positive reaction on a skin prick test was reduced (adjusted odds ratio, 0.43; 95% CL, 0.23-0.79, P = .007), and the concentration of cat-specific IgE was less (25% less; 95% CI, 43% to 2.3% less; P = .033) in sera from very-low-birth-weight subjects compared with that seen in sera from control subjects. Within the very-low-birth-weight group, those born at an earlier gestational age were less likely to have positive skin prick test reactions (adjusted odds ratio for 1 week, 0.82; 95% CI, 0.68-0.98, P = .029) and less likely to have high levels of allergen-specific IgE. Cumulative incidences of atopic disease were similar between adults of very low birth weight and control subjects. Conclusions: Young adults born prematurely and at very low birth weight have a lower incidence of atopy than adults who were born full term. This finding supports the hypothesis that the risk for atopy is determined during early stages of development. (J Allergy Clin Immunol 2011;127:935-42.)