Preterm birth linked to reduced risk for atopy in adulthood
MedWire News: Results from a Finnish study suggest that individuals born prematurely with a very low birth weight have a reduced risk for atopy in adulthood compared with those born at full term.
Writing in the Journal of Allergy and Clinical Immunology, Eero Kajantie (National Institute for Health and Welfare, Helsinki) and team explain that immunologic pathways are primed in early life and preterm birth may influence this process and an individual's risk for atopy in later life.
But they add that previous studies investigating the risk for atopy among individuals born prematurely have produced inconclusive results, and mainly included participants who were born moderately preterm.
To investigate further, the team studied data on 166 adults who were born severely preterm. with a mean gestational age of 29.2 weeks and with a very low mean birth weight of 1120 g. A group of 172 adult controls who were born at full term, with a mean gestational age of 40.1 weeks and a mean birth weight of 3593 g, and who were matched for gender, age, and birth hospital were included for comparison purposes.
All of the participants were assessed for atopic predisposition between the ages of 18 and 27 years using skin prick tests for six common aeroallergens; birch, timothy grass, mugwort, cat, dog, and Dermatophagoides pteronyssinus (house dust mite).
In addition, blood samples were collected from the participants and assessed for concentrations of total immunoglobulin (Ig)E and three types of allergen-specific IgE (cat, birch, and timothy grass).
The participants were also asked whether they had ever received a diagnosis of asthma, allergic rhinitis, or atopic eczema.
After accounting for factors such as parental atopy, parental education, number of siblings, maternal smoking during pregnancy, current smoking, pet ownership, and body mass index, the researchers found that individuals with a preterm birth were a significant 57% less likely to have at least one positive reaction on a skin prick test than controls.
Individuals born preterm also had lower serum concentrations of any type of allergen-specific IgE compared with controls, at an adjusted odds ratio (OR) of 0.48. For example, the mean concentration of IgE for cat allergen was a significant 25% lower in preterm individuals than controls.
Furthermore, among individuals born prematurely, those with a lower gestational age were less likely to have positive skin prick test results and elevated levels of allergen-specific IgE than those with a higher gestational age.
There was no difference between participants born prematurely and controls regarding the cumulative incidence of atopic diseases, however.
Kajantie and team conclude: "Although severe preterm birth has been associated with many disadvantages in later life, not all outcomes are unfavourable... Young adults born prematurely and at very low birth weight have a lower incidence of atopy than adults who were born full term."
They add: "This finding supports the hypothesis that the risk for atopy is determined during early stages of development."
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By Mark Cowen