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Time trends in repeated spirometry in children
1Dept of Epidemiology and Public Health, University of Wageningen, The Netherlands.
Insights
Pulmonary function tests in children revealed unexpected time-dependent changes, independent of air pollution. These lung function trends, including peak expiratory flow (PEF) and forced vital capacity (FVC), must be considered in air pollution studies.
Area of Science:
- Environmental Health
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Repeated pulmonary function testing is crucial for assessing acute health effects of air pollution.
- Understanding baseline lung function trends in children is essential for accurate exposure assessment.
- Previous studies have not fully accounted for time-dependent variations in spirometry independent of environmental factors.
Purpose of the Study:
- To investigate time-dependent trends in spirometric variables in children, independent of air pollution.
- To determine if these trends differ based on testing intervals.
- To inform the methodology of future air pollution impact studies on respiratory health.
Main Methods:
- Spirometry was performed 6-10 times over ~3 months in 1,621 children aged 7-11 years.
- Pulmonary function data, including peak expiratory flow (PEF), maximal mid-expiratory flow (MMEF), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1), were analyzed.
- Children were divided into groups based on testing intervals (1 week vs. 3 weeks) to assess the impact of frequency.
Main Results:
- Peak expiratory flow (PEF) showed a greater than expected increase over time.
- Maximal mid-expiratory flow (MMEF) exhibited a decrease with time.
- Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) demonstrated smaller than expected increases.
- Deviations were more pronounced in children tested weekly compared to those tested bi-weekly.
- Time-dependency relationships were non-linear for FVC/FEV1 and approximately linear for PEF/MMEF.
Conclusions:
- Significant, unexpected time-dependent changes in pulmonary function occur in children.
- These spirometric trends vary by lung function parameter and testing frequency.
- Accounting for these intrinsic temporal variations is critical for accurately interpreting air pollution effects on respiratory health in longitudinal studies.
Abstract:
In a study on acute health effects of air pollution in the Netherlands, pulmonary function has been measured repeatedly in children aged 7-11 yrs. In study periods of approximately 3 months, 6-10 tests have been made in a group of 1,621 children. The spirometric data have been examined for the presence of trends of pulmonary function with day of study, independent of air pollution. Peak expiratory flow (PEF) increased more than expected from normal lung growth, whereas for maximal mid-expiratory flow (MMEF) a decrease with time was observed. For forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) a smaller than expected increase with time was observed. The observed deviation from the expected pattern was larger for the children with a one week interval between successive tests than for the children with a three week interval. For FVC and FEV1 a non-linear relationship with time was observed, for PEF and MMEF this relationship was approximately linear. The particular changes of spirometric variables with time need to be taken into account when repeated lung function tests are performed to investigate acute effects of air pollution exposure.