[Trends in the prevalence rate of wheezing in school children]

Questionnaire surveys of children in all public primary schools in Osaka Prefecture have been conducted every other year from 1975 to 1993 (10 times in total). The number of schools ranged from 848 to 1,009 and those of the pupils from 514,656 to 871,008 (7,128,443 in total responded to each survey). 1. The prevalence rate of wheezing was 3.0 +/- 0.1% which was almost constant during the period, 1975-1983 and thereafter increased to reach 4.7% in 1993. The rate for 1st-graders was highest early in the period, but the rate increased with grade since about 1985, resulting in a lack of prevalence difference among the 1st to 5th graders. 2. Their persistent conditions of wheezing were investigated according to the individual questionnaires. The increase in the prevalence rate from 1985 was found to be caused by the lowering in the remission rate of wheezing in addition to the increases in persistent states and new developments of the symptoms. 3. Aiming to clarify the correlation between the prevalence rate and the air pollution in their places of residence, the prevalence rate was compared among various areas. The rates were slightly higher in the business and industry area than the residential ones in the suburbs, but increase in the prevalence rate from 1985 was commonly found in the respective areas.