A Study on Mediation by Offspring BMI in the Association between Maternal Obesity and Child Respiratory Outcomes in the Amsterdam Born and Their Development Study Cohort.
BACKGROUND
A causal relationship between maternal obesity and offspring asthma is hypothesized to begin during early development, but no underlying mechanism for the found association is identified. We quantitatively examined mediation by offspring body mass index (BMI) in the association of maternal pre-pregnancy BMI on risk of asthma and wheezing during the first 7-8 years of life in a large Amsterdam born birth cohort.


METHODS
For 3185 mother-child pairs, mothers reported maternal pre-pregnancy BMI and offspring outcomes "ever being diagnosed with asthma" and "wheezing in the past 12 months" on questionnaires. We measured offspring height and weight at age 5-6 years. We performed a multivariate log linear regression comparing outcomes in offspring of mothers with different BMI categories. For each category we quantified and tested mediation by offspring BMI and also investigated interaction by parental asthma.


RESULTS
At the age of 7-8 years, 8% of the offspring ever had asthma and 7% had current wheezing. Maternal pre-pregnancy obesity was associated with higher risks of asthma (adjusted RR 2.32 (95% CI: 1.49-3.61) and wheezing (adjusted RR 2.16 (95% CI: 1.28-3.64). Offspring BMI was a mediator in the association between maternal BMI and offspring wheezing, but not for asthma. There was no interaction by parental asthma.


CONCLUSIONS
Maternal pre-pregnancy obesity was associated with higher risks of offspring asthma and wheezing. The association between maternal obesity and offspring wheezing was both direct and indirect (mediated) through the child's own BMI.
Department of Public Health, Academic Medical Center, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands.
Margreet W
MW
Harskamp-van Ginkel
Epidemiology Branch and Laboratory of Respiratory Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, Durham, North Carolina, United States of America.
Stephanie J
SJ
London
Department of Chronic Diseases, Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
Maria C
MC
Magnus
Department of Public Health, Academic Medical Center, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands.
Maaike G
MG
Gademan
Department of Public Health, Academic Medical Center, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands.
Tanja G
TG
Vrijkotte
D000328:Adult; D001249:Asthma / Q000209:etiology* / Q000503:physiopathology; D001724:Birth Weight; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D009035:Mothers; D009426:Netherlands; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000503:physiopathology*; D012135:Respiratory Sounds / Q000209:etiology* / Q000503:physiopathology