[The relapse rate in patients with bronchial asthma remission and the risk factors of relapse]

To investigate the relapse rate in patients with bronchial asthma remission, a questionnaire study was performed. The answer sheets from 450 of 865 patients who first visited Saitama Medical School Hospital before the age of 16 were obtained. 281 patients had been in asthma remission more than one year after the last their attack. Among them, 31 patients (14 males and 17 females) relapsed. Their average age of last attack was 15.1 +/- 3.6 years old. While the average age of the last attack in patients who did not relapse was 12.9 +/- 4.1. The average age of relapse was 20.8 +/- 4.2 and their duration of remission was 5.8 +/- 2.9 years. No relapse was observed after 14 years of remission. The most of the patients relapsed within 10 years. The relapse rate calculated by life table method was 13.5%. Relapse retes were calculated in various characteristics: females; 24.9%, patients who had severe symptoms at the first visit and moderately severe; 22.4%, 23.1%, respectively, positive history of steroid therapy; 25.1%, IgE level of more than 500 IU/ml; 19.7%, patients whose last attack was after the age of 13; 21.2%. Those figures are significantly higher than the opposite characteristics. The environmental factors significantly contribute to the relapse of remitted asthmatics. They are apartment house, ferroconcrete and aluminum-framed house, carpet in bedroom, pets, maternal or self-smoking. The asthmatic children who have those risk factors should be followed to prevent relapse and their environment controls should be adequately stressed even in asthma remission.