You are here

Impact of exposure to air pollution on asthma; A multi-exposure assessment

Principal Investigator: 

University of Copenhagen, Denmark

This New Investigator Award study will evaluate whether air pollution is associated with increased incidence of asthma in 3 cohorts in Denmark.

Funded under

Abstract for the 2019 HEI Annual Conference

Maternal Smoking during Pregnancy and Asthma in Children and Young Adults

Marie Pedersen1;2, Katrine Facius1, Zorana J Andersen1, Anne-Marie Nybo Andersen1, Xavier Basagaña3, Hans Bisgaard4, Jørgen Brandt5, Esben Budtz-Jørgensen1, Klaus Bønnelykke4, Casper-Emil Pedersen4, Lise Frohn5, Leslie Stayner6, Matthias Ketzel5, Bert Brunekreef7, Steffen Loft1

1University of Copenhagen, Copenhagen, Denmark; 2Danish Cancer Society Research Center, Copenhagen, Denmark; 3Barcelona Institute of Global Health, Barcelona, Spain; 4Gentofte Hospital, Copenhagen, Denmark; 5Aarhus University, Roskilde, Denmark; 6University of Illinois at Chicago, USA; 7Utrecht University, Utrecht, the Netherlands

Background. Asthma is a common disease with a heterogeneous etiology. The role of ambient air pollution on asthma development is unclear, as multiple factors starting from fetal life may be involved. Some of these factors may be correlated or share sources and pathways resulting in joint effects that are greater than additive. Thus, the potential for confounding and modification of the air pollution exposure effects on asthma by maternal smoking during pregnancy is very high.

Objectives. To prepare for our HEI funded study on air pollution and asthma, we examined the associations between maternal smoking during pregnancy and asthma. We examined different definitions of asthma since the severity can range from intermittent to severe disease.

Methods. We included all live-born children born to women with singleton pregnancies in Denmark without infant death or emigration during 1997 to 2016. We used the unique personal identification number for data linkage and to extract information about asthma and personal characteristics from population-based registries. We defined a prescription case of asthma as (1) a child who had redeemed any type of anti-asthmatic drug except for beta2-agonists as liquid, inhaled beta2-agonists only once or inhaled steroid only once, and (2) a hospitalization case of asthma as a child who had a registered asthma diagnosis. For both definitions, only the first registered case was used. We also categorized asthma into three distinct phenotypes for children born before 2002; early transient as having asthma only during ages 4-6, but not thereafter, persistent as having asthma during 4-6 years of age and still having asthma during 14-19 years of age and adolescent-onset as having asthma after, but not before age 14. Odds ratios (ORs) for asthma associated with smoking were estimated using adjusted logistic regression with generalized estimating equations (GEE).

Results. Out of the 1,156,878 children, 32.4% had asthma according to redeemed prescriptions and 6.4% had a diagnosis from the hospitalization registry. Overall, 14.0% of the mothers smoked and the prevalence of smoking decreased over time (21.4% in 1997-2001 vs. 8.4% in 2012-2016). Any smoking during pregnancy was associated with increased odds of asthma at any age (adjusted ORs and the 95% confidence intervals were 1.38 (1.35, 1.41) and 1.41 (1.40, 1.43) for prescription and hospitalization, respectively). Increased odds were evident for early transient and persistent asthma, but not for adolescent-onset asthma.

Conclusions. These preliminary findings support existing evidence that links maternal smoking during pregnancy with increased risk of asthma development. We plan to examine the independent and combined effects of air pollution and smoking when the data are available.


Poster by Pedersen et al., 2019 HEI Annual Conference