Epidemiology of Japanese Cedar Pollinosis

Abstract

The present situation and future aspects in epidemiological studies of Japanese cedar pollinosis are discussed. First of all, diagnostic criteria for epidemiological studies have not been established. A study group supported by the Ministry of Health and Welfare produced a criterion in March 1992, however, we produced other criterion compensating for the former's defects. Our criterion is as follows; any nasal and/or conjunctival symptom continuing for three weeks or more in March and/or April, and positive serum IgE against Japanese cedar pollen. A tentative study was performed. According to the former criterion, prevalence rates of “definite pollinosis” were 8.3% in adults and 5.6% in children, while those of “definite and probable pollinosis” were 16.8% and 12.1%, respectively. Prevalence rates according to our criterion were 14.1% and 9.0%, respectively.
Symptomatic criteria were defined as corresponding epidemiological criteria e x cept for serum examinations, and validity of symptomatic criteria was tested. Sensitivities for all criteria were 100% theoretically. Specificities for “definite pollinosis” of the study group criteria were 96.8% in adults and 97.0% in children. Those for “definite and probable pollinosis” were 88.3% and 90.3%, respectively. Those for our criteria were 89.2% in both sample groups. If the validity of these criteria are stable in other study samples, prevalence rates can be estimated by only questionnaire surveys.
Risk factors of Japanese cedar pollinosis are not epidemiologically established although many candidate factors have been discussed in clinical fields. Methodological problems for case-control study are the following. Three types of case should be concerned; symptomatic patient, sensitized person including symptomatic patient, and sensitized but asymptomatic person. When the case involves a symptomatic patient, bias and confounding originating from the following types of control are a concern; a) not sensitized and asymptomatic people, b) asymptomatic people without serum examination, c) not sensitized people with or without allergic-like symptoms. The largest problem for cohort study is the need to start in childhood because sensitization during early life is assumed.