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. 2013 Jan;110(1):18-23.
doi: 10.1016/j.anai.2012.10.010. Epub 2012 Nov 10.

Population-based study on association between birth weight and risk of asthma: a propensity score approach

Hyeon J Yang  1 , Rui Qin, Slavica Katusic, Young J Juhn
Affiliations

Population-based study on association between birth weight and risk of asthma: a propensity score approach

Hyeon J Yang et al. Ann Allergy Asthma Immunol. 2013 Jan.

Abstract

Background: Previous studies that assessed the role of birth weight in the risk of asthma have been limited because of selection bias and covariate imbalance.

Objective: To assess the association between birth weight and risk of asthma by applying a propensity score approach.

Methods: The study was designed as a retrospective cohort study based on a birth cohort of children born between January 1, 1976, and December 31, 1979, in Rochester, Minnesota. The propensity scores for birth weight were formulated using 16 covariates. We matched the propensity scores for children having low birth weight (<2,500 g) within a caliper of 0.2 SD of logit function of propensity scores. We calculated the cumulative incidence of asthma between low and normal birth weight groups using the Kaplan-Meier curve.

Results: There were 3933 eligible children born between January 1, 1976, and December 31, 1979. Before matching, 13 of the 193 children (6.7%) born weighing 2,500 g developed asthma, whereas 201 of the 3,740 children (5.4%) born weighing 2,500 g and above developed asthma (P=.42). There were significant covariate imbalances between comparison groups. However, after propensity score matching, covariate imbalance was significantly reduced, and children born weighing less than 2,500 g had a similar risk to matched children born with normal birth weight (8.3% vs 7.3%, P=.75).

Conclusion: Birth weight is not associated with risk of asthma during the first 6 years of life. The propensity score may be a useful method for observational studies concerning asthma epidemiology.

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Conflict of interest statement

The study investigators have nothing to disclose that poses a conflict of interest.

Figures

FIGURE 1
FIGURE 1
Kaplan-Meier plot of the cumulative incidence of asthma between low birth weight group (<2500 g) and normal birth weight group (≥2500 g) during the first seven years of life (p=0.746 based on log-rank test)
See this image and copyright information in PMC

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