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Morning-to-evening variation in exercise-induced bronchospasm
Elcio O Vianna1, Luiz C Boaventura, João Terra-Filho
1Department of Medicine, University of São Paulo Medical School at Ribeirão Preto, Av. Bandeirantes, 3900 Ribeirão Preto--SP 14048 900, Brazil.
The Journal of Allergy and Clinical Immunology
|August 10, 2002
Summary
Exercise-induced bronchospasm (EIB) is less severe in the morning for asthma patients. Baseline airway caliber influences EIB intensity, which is higher in the evening.
Area of Science:
- Pulmonology
- Exercise Physiology
- Chronobiology
Background:
- Exercise is a common trigger for asthma symptoms.
- Exercise-induced bronchospasm (EIB) severity is influenced by factors like hyperventilation.
- The impact of time of day on EIB has not been well-documented.
Purpose of the Study:
- To compare the intensity of EIB between morning and evening exercise challenges.
- To assess differences in minute ventilation (VE) during exercise at different times of day.
Main Methods:
- Twenty-two asthma patients and 12 controls underwent exercise challenges at 7 am and 6 pm.
- The order of the challenges was randomized, with the second challenge within one week.
- Primary outcomes measured were EIB intensity (maximal fall in FEV1) and VE.
Main Results:
- Asthma patients showed significantly lower EIB in the morning (14.8%) compared to the evening (21.4%).
- Morning exercise resulted in higher minute ventilation (55.4 L/min) than evening exercise (52.4 L/min).
- Baseline FEV1 was higher in the evening, correlating with EIB intensity, unlike in the morning.
Conclusions:
- The diurnal variation in baseline airway caliber contributes to enhanced EIB in the evening.
- These findings highlight the importance of the time of day in managing exercise-induced asthma.
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