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Diurnal variation in lung function in subgroups from two Dutch populations: consequences for longitudinal analysis
G J Borsboom1, W van Pelt, H C van Houwelingen
1Departments of Physiology and Medical Statistics, Leiden University, Leiden, The Netherlands.
Summary
Circadian rhythms significantly impact pulmonary function measurements like forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). Accounting for daily variations is crucial for accurate long-term lung health assessments.
Area of Science:
- Pulmonary Medicine
- Chronobiology
- Epidemiology
Background:
- Pulmonary function tests (PFTs) are essential for diagnosing and monitoring respiratory diseases.
- Diurnal variations in lung function are known but their impact on longitudinal studies needs quantification.
- Understanding circadian rhythms in PFTs is vital for accurate interpretation of lung health trends.
Purpose of the Study:
- To investigate the circadian variation of key pulmonary function parameters (FVC, FEV1, PEF, TLC, VC, RV).
- To analyze how diurnal variations affect the estimation of longitudinal changes in lung function.
- To identify subgroups with potentially greater diurnal variability in PFTs.
Main Methods:
- Longitudinal study of 876 adults across four surveys from 1975-1985 in the Netherlands.
- Measurements of FVC, FEV1, PEF, TLC, VC, and RV taken between 9:00 AM and 9:00 PM.
- Analysis of diurnal patterns and their influence on estimated longitudinal declines, considering subgroups.
Main Results:
- FVC, FEV1, PEF, and VC peaked around noon, while RV decreased from morning to noon; TLC remained stable.
- Average diurnal variation was notable for FVC (4.8%), FEV1 (2.8%), and PEF (3.1%), suggesting circadian airway changes.
- Younger adults, smokers, and those with respiratory symptoms exhibited significantly larger diurnal changes.
Conclusions:
- Diurnal variation in pulmonary function is significant and can influence longitudinal change estimates.
- Adjustment for diurnal variation slightly reduces residual standard deviations of estimated longitudinal declines.
- Random measurement times (≥3 visits) or measurements after 11:00 AM minimize the impact of diurnal variation on average longitudinal decline.