Time trend in the prevalence of adult asthma in Japan: findings from population-based surveys in Fujieda City in 1985, 1999, and 2006.

Background: The burden of asthma is recognized as an important public health problem worldwide. In most countries, the prevalence of asthma has been reported to increase in the last few decades. However, more recent epidemiological studies have shown that the prevalence of asthma has been flat or even decreasing after the 1990 s in some developed countries. The recent time trend in the prevalence of adult asthma in Japan is unknown.
Methods: Population-based surveys were conducted three times in the same region, in 1985, 1999, and 2006, at Fujieda City, Shizuoka, Japan, and the results were reported previously. We compared the results of these surveys to reveal the time trend in the prevalence of adult asthma. Although the questionnaires used in these surveys were not exactly the same, the time trend was assessed by comparing the responses to relevant questions between questionnaires.
Results: The prevalences of wheeze following a common cold and dyspneal feeling at night increased significantly from 1985 to 1999 (4.2% to 7.6%, and 3.2% to 5.3%, respectively). The prevalences of lifetime asthma and current asthma also significantly increased from 1999 to 2006 (5.1% to 6.7%, and 1.5% to 3.4%, respectively).
Conclusions: The prevalences of asthma among adults in Fujieda City consistently increased from 1985 to 2006. There was no evidence that the prevalences were in plateau or decreasing. These findings suggest that more efforts are required to stop the increase in the burden of this disease in Japan.