Parental asthma and risk of offspring asthma from childhood to adolescence: a population-based cohort study

BACKGROUND: Maternal asthma has been associated with a higher risk of asthma in early childhood compared with paternal asthma, but it is unclear whether this difference persists into adolescence. METHODS: We analysed 55 643 children from the Norwegian Mother, Father and Child Cohort Study. Parental asthma was self-reported during pregnancy; offspring asthma was reported by mothers at ages 3, 7 and 14 years. Logistic regression models estimated associations between parental asthma and offspring asthma at each age, adjusting for maternal age, parental prepregnancy body mass index, parental education, parental smoking and parental atopic conditions, including atopic eczema and pollen/hay fever. RESULTS: Asthma prevalence among offspring was 6.5% at age 3, 5.2% at age 7 and 5.4% at age 14. Compared with children of non-asthmatic parents, adjusted ORs for asthma at age 3 were 3.11 (95% CI 2.73 to 3.54) for maternal asthma only and 2.25 (95% CI 1.97 to 2.56) for paternal asthma only. Similar patterns were observed at ages 7 (maternal OR 2.96 (95% CI 2.54 to 3.45); paternal OR 2.36 (95% CI 2.03 to 2.75)) and 14 (maternal OR 3.03 (95% CI 2.46 to 3.73); paternal OR 1.95 (95% CI 1.57 to 2.43)). At age 3, maternal asthma was associated with higher odds in boys (OR 3.30) than girls (OR 2.82), and higher absolute risk (19.2% vs 12.2%). However, interaction tests by offspring sex were not statistically significant. CONCLUSIONS: Maternal asthma conferred a consistently stronger risk of offspring asthma than paternal asthma, from early childhood into adolescence. This effect appeared slightly stronger in boys in early childhood, though sex differences were not statistically significant.