Published ahead of print on February 8, 2007, doi:10.1164/rccm.200610-1441OC
© 2007 American Thoracic Society doi: 10.1164/rccm.200610-1441OC
Respiratory Symptoms in the First 7 Years of Life and Birth Weight at TermThe PIAMA Birth Cohort1 Department of Pediatrics/Respiratory Medicine, Erasmus University, Rotterdam, The Netherlands; 2 Departments of Chronic Disease Epidemiology and Infectious Diseases Epidemiology, National Institute of Public Health and the Environment, Bilthoven, The Netherlands; 3 Institute for Risk Assessment Sciences, University of Utrecht, Utrecht, The Netherlands; 4 Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands; 5 Department of Epidemiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; 6 Centre for Pediatric Allergology, Wilhelmina Children's Hospital, Utrecht, The Netherlands; and 7 Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands Correspondence and requests for reprints should be addressed to Prof. dr. J.C. de Jongste, M.D., Ph.D., Erasmus MC/Sophia Children's Hospital, Department of Pediatric Respiratory Medicine, P.O. Box 2060, 3000 CB Rotterdam, The Netherlands E-mail: j.c.dejongste{at}erasmusmc.nl Rationale: The relation between birth weight and respiratory symptoms and asthma in children remains unclear. Previous studies focused on a relation at separate ages. A longitudinal analysis may lead to a better understanding. Objectives: To estimate the effect of birth weight on the development and course of respiratory symptoms and asthma in the first 7 years of life. Methods: In a prospective birth cohort study, 3,628 children with a gestational age 37 weeks or more were monitored for 7 years. Parental questionnaires were used to assess respiratory health yearly. Associations of birth weight with respiratory symptoms (wheezing, coughing, respiratory infections) and doctor's diagnosis of asthma were assessed in a repeated-event analysis. Measurements and Main Results: Lower birth weight was associated with more respiratory symptoms (odds ratio [OR] per kg decrease in birth weight, 1.21; 95% confidence interval [CI], 1.091.34). The effect of birth weight increased from age 1 to 5, but decreased thereafter and was no longer significant at the age of 7. The effect of birth weight on respiratory symptoms was significantly greater among children exposed to tobacco smoke in their home than among nonexposed children (OR at 5 yr: 1.21 [95% CI, 1.021.44] and 1.52 [95% CI, 1.231.87], respectively). Birth weight and a doctor's diagnosis of asthma were not related (OR, 1.06; 95% CI, 0.821.37). Conclusions: A lower birth weight in children born at term is associated with a transiently increased risk of respiratory symptoms. This effect is enhanced by environmental tobacco smoke exposure.
Key Words: birth weight environmental tobacco smoke respiratory symptoms longitudinal analysis children
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