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Lung function, pre- and post-natal smoke exposure, and wheezing in the first year of life
I B Tager1, J P Hanrahan, T D Tosteson
1Department of Medicine, University of California, San Francisco.
Insights
Infants with lower initial lung function, specifically reduced expiratory flow, experienced more lower respiratory illnesses (LRI). This association was stronger in female infants, particularly those whose mothers did not smoke during pregnancy.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Infant Health
Background:
- Infant lung function is a critical determinant of respiratory health.
- Early identification of risk factors for lower respiratory illness (LRI) is essential for timely intervention.
- Maternal smoking during pregnancy is a known risk factor for adverse infant respiratory outcomes.
Purpose of the Study:
- To investigate the relationship between initial pulmonary function measurements in infants and the subsequent development of wheezing and LRI.
- To determine if maternal prenatal smoking influences this relationship.
- To assess the impact of postnatal environmental tobacco smoke exposure.
Main Methods:
- Pulmonary function tests (PFTs), including partial expiratory flow-volume curves and functional residual capacity (FRC), were performed on 97 infants before 6 months of age.
- LRI occurrence was monitored through standardized questionnaires, telephone calls, and physician visit reviews.
- Maternal prenatal smoking was assessed using urine cotinine levels and questionnaires.
Main Results:
- Infants who developed LRI had significantly lower preillness length-corrected forced expiratory flow at FRC (VFRC) compared to those without LRI.
- This difference was most pronounced in female infants whose mothers did not smoke during pregnancy.
- Maternal wheezing history was more common in infants with LRI, independent of smoking status.
Conclusions:
- Lower initial VFRC is associated with an increased frequency of LRI in infants.
- Female infants may be particularly susceptible to the effects of reduced lung function on LRI risk.
- Early PFTs could potentially identify infants at higher risk for respiratory illnesses.
Abstract:
The relationship between initial level of lung function and subsequent wheezing, lower respiratory illness (LRI) was studied in 97 infants in whom the first measurement of pulmonary function (PFT) was made before 6 months of age. Occurrence of LRI was evaluated by standardized questionnaires at each well-baby visit, biweekly telephone calls to mothers, and review of all visits to physicians. Infant PFT was assessed by partial expiratory flow-volume curves and helium-dilution measurement of functional residual capacity (FRC). Maternal, prenatal smoking was assessed by urine cotinine and standard questionnaires. Infants who developed an LRI during the first year of life had lower preillness length-corrected forced expiratory flow at FRC (VFRC) than those who did not experience an LRI (males, 2.06 +/- 0.20 versus 2.32 +/- 0.29 ml/s/cm; females, 2.38 +/- 0.20 versus 2.91 +/- 0.26 ml/s/cm). Similar results were observed with FRC-corrected VFRC. No differences were observed for FRC. Differences in lung function were greatest in female infants whose mothers did not smoke during pregnancy (VFRC 2.67 +/- 0.25 versus 3.49 +/- 0.26 ml/s/cm for those with and without LRI, respectively; p = 0.03). History of maternal wheezing was more common in infants who experience an LRI, independent of maternal smoking. The results were not influenced by exposure to nonmaternal sources of environmental tobacco smoke in the postnatal period. Regression analyses that included data for multiple measurements of VFRC over the first year and took account of duration of follow-up demonstrated that lower levels of VFRC were associated with an increased frequency of LRI, especially in female infants.(ABSTRACT TRUNCATED AT 250 WORDS)