Background: The importance of smoking in bronchial asthma has been thoroughly investigated. Although a high smoking rate has been recognized in Japan, there have been few studies of the relationship between active smoking and bronchial asthma, and little analysis of the gender difference in this relationship. The aims of this study were to examine the contribution of active smoking to asthma and to clarify any gender difference.
Methods: For 8 weeks from September through October 2000, a smoking questionnaire survey was performed on adult patients with bronchial asthma, and their attending physicians, in Niigata Prefecture, Japan. The questionnaire surveyed asthma control, asthma-related emergencies and satisfaction in daily life. The attending physicians were questioned about patient profiles and medications. Patients were classified into three groups: non-smokers (NS), ex-smokers (ES) and current smokers (CS). For examination of gender differences, the CS group was compared with the NS group, due to variable duration of smoking and of cessation of smoking in the ES group.
Results: Complete data were received from 2947 cases. Of the male patients, 340 (23.0%) were in the CS group, 325 (22.0%) were in the NS group and 812 were in the ES group. Of the female patients, 109 (7.4%) were in the CS group, 1132 (77.4%) were in the NS group, and 229 (7.4%) were in the ES group. The male CS group had more severe asthma-related symptoms in the morning and at night, more sputum and cough in the morning, and more severe sleep disturbance than the male NS group. In the female patients, these differences were not detected. A logistic and multiple regression analysis confirmed these significant differences between male and female asthma patients.
Conclusions: The gender differences in the susceptibility of asthma to smoking suggests the need for gender-specific strategies for smoking cessation, although further investigation is required.

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