Published ahead of print on February 8, 2007, doi:10.1164/rccm.200610-1441OC Am. J. Respir. Crit. Care Med., Volume 175, Number 10, May 2007, 1078-1085 A more recent version of this article appeared on May 15, 2007
Submitted on October 9, 2006 Respiratory Symptoms in the First 7 Years of Life and Birth weight at Term - The PIAMA Birth CohortDaan Caudri1,1 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 Institute for Risk Assessment Sciences, University of Utrecht, Utrecht, The Netherlands; Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands, 5 Department of Epidemiology, University Medical Center Groningen, Groningen, The Netherlands, 6 Centre for Paediatric Allergology, Wilhelmina Children's Hospital, Utrecht, The Netherlands, 7 Beatrix Children's Hospital, University Medical Center Groningen, Groningen, The Netherlands * To whom correspondence should be addressed. 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.
Objective
To estimate the effect of birth weight on the development and course of respiratory symptoms and asthma in the first seven years of life.
Methods
In a prospective birth cohort study 3628 children with a gestational age Key words: birth weight, respiratory symptoms, environmental tobacco smoke, longitudinal analysis, children
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37 weeks were followed 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.
Main results
Lower birth weight was associated with more respiratory symptoms (Odds Ratio per kilo decrease in birth weight: 1.21; 95% Confidence Interval: 1.09-1.34). 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 non-exposed children, OR at 5: 1.21 (1.02-1.44) and 1.52 (1.23-1.87), respectively. Birth weight and a doctors' diagnosis of asthma were not related: OR: 1.06 (0.82-1.37).
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.
