Tue Sep 24, 2002
NEW YORK (Reuters Health) - Asthma patients who experience wheezing, chest tightness or difficulty breathing when they exercise may have worse lung function in the evening than in the morning, according to new study findings.
Exercise type, environmental conditions, asthma severity and pre-exercise treatment are all known to influence the occurrence and severity of these problems, known as exercise-induced bronchospasm, Dr. Elcio O. Vianna from the University of Sao Paulo in Brazil, and colleagues note. In contrast, relatively little attention has been given to the effect that time of day has on the condition.
In the current study, the researchers conducted exercise tests in 22 people with asthma and 12 healthy ("control") patients at 7 AM and 6 PM. The intensity of the lung spasms were graded during exercise according to the maximum fall in a measure of lung-function known as forced expiratory volume. The findings are published in the August issue of the Journal of Allergy and Clinical Immunology.
For asthmatic patients, lung function problems were more likely in the evening than in the morning. The exercise-induced lung spasm scores were 14.8% in the morning compared with 21.4% in the evening. No changes related to the time of day were seen in the control group of healthy patients.
The current findings suggest that exercise-related asthma tests may not be accurate if performed in the morning.
"The time of day that an exercise challenge is performed might interfere with the yield of the test," the authors state.
SOURCE: Journal of Allergy and Clinical Immunology 2002;110:236-240.