Preterm birth and low birth weight continue to increase the risk of asthma from age 7 to 43

Background: Perinatal events can influence the development of asthma in childhood but current evidence is contradictory concerning the effects on life-time asthma risk. Objective: To assess the relationship between birth characteristics and asthma from childhood to adulthood. Methodology: All available birth records for the Tasmanian Longitudinal Health Study (TAHS) cohort, born in 1961 were obtained from the Tasmanian State Archives and Tasmanian hospitals. Low birth weight (LBW) was defined as less than 2500 grams. Preterm birth was defined as delivery before 37 weeks' gestation. Small for gestational age (SGA) was defined as a birth weight below the 10^th percentile for a given gestational age. Multivariate logistic and cox regression were used to examine associations between birth characteristics and lifetime risk of current and incident asthma, adjusting for confounders. Results: The prevalence of LBW was 5.2%, SGA was 13.8% and preterm was 3.3%. LBW (OR = 1.65, 95%CI 1.12,2.44) and preterm birth (OR = 1.81, 95%CI 0.99, 3.31) were both associated with an increased risk of current asthma between the ages of 7 to 43 years. There was no association between SGA and current asthma risk. However, SGA was associated with incident asthma (HR = 1.32, 95%CI 1.00, 1.74), and there was an interaction with sex (p value = 0.08), with males having a greater risk of incident asthma (HR = 1.70, 95%CI 1.16–2.49) than females (HR = 1.04, 95%CI 0.70–1.54). Conclusions: Preterm birth and LBW were associated with an increased risk of current asthma into middle-age. These findings are the first to demonstrate the continuing impact of these characteristics on asthma risk into middle-age.