Abstract
Background: Circadian rhythm is a well recognized feature of patients with asthma characterized by a morning dip of the peak flow rate. However, evening dips of asthmatic patients have never been systematically studied.
Methods: We prospectively studied the frequency and clinical characteristics of asthma patients with evening dips. The records of 229 patients for two months were analyzed.
Results: Fifty four patients (23.6%) had repeated evening dips. Comparison of the groups with or without evening dips revealed that the group of patients with evening dips were younger (mean age, 47.3) and had higher asthma steps (mean 2.46) compared to the other group (56.2 and 1.93, respectively). Self-reported causes of evening dips were related to work overload (24.1 %), exercise (9.3%), mental stress (7.4%), allergen exposure (5.5%), cold air (3.7 %), alcohol (3.7%), and unknown (38.8%). Evening dips of peak flow are often related to the daily activity of patients.
Conclusions: Detection of evening dips might be useful to give specific advices to the patients, and be helpful for the prevention and control of asthma exacerbation.
