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Low birth weight not associated with increased risk for childhood asthma
There was no link between low birth weight and an increased risk for children developing asthma within the first 7 years of life, according to recent study results.
Researchers in Rochester, Minn., conducted a retrospective cohort study of 3,933 children born between January 1976 and December 1979 to compare incidence of childhood asthma between low birth weight and normal birth weight newborns. One hundred ninety-three children had low birth weight (less than 2,500 g), and 3,740 were considered of normal birth weight (2,500 g or more).
To reduce covariate imbalance between groups, researchers applied 16 variables to devise a propensity score for developing asthma. Variables included gestational age, sex, race, parents’ age and educational level at child’s birth, smoking during pregnancy, number of prenatal visits, pregnancy complications and other criteria. Once assessed, researchers used the Kaplan-Meier curve to calculate cumulative incidence of asthma between groups.
In unmatched analysis, 13 (6.7%) of the low birth weight children developed asthma during the first 7 years of life compared with 201 (5.4%) of the children born at normal weight (P=.42). Using exact propensity scores, researchers paired 109 low birth weight children with an equal number of those born at normal weight. Of them, nine low birth weight (8.3%) and eight normal birth weight (7.3%) children developed asthma, resulting in a similar risk (P=.75).
“Low birth weight is not associated with a subsequent risk of developing childhood asthma,” the researchers concluded. “We suggest that the propensity score approach may be a useful method to reduce covariate imbalance in observational studies concerning asthma epidemiology.”
