Abstract
Objectives It has been reported that morbidity from allergic rhinitis in the National Health Insurance records in Ibaraki Prefecture for May correlated with the quantity of Japan cedar pollen scattered in each year.
The purpose of the present investigation was to clarify the Japanese cedar pollinosis contribution to morbidity, and also clarifying the influence of air pollution and medical resources on the crisis and symptoms of allergic rhinitis.
Methods The charts in four otolaryngology facilities were used for analyzing the Japan cedar pollinosis content with reference to the allergic rhinitis during the pollen season.
The age-adjusted morbidity of allergic rhinitis was annually compared employing data of National Health Insurance records for medical examinations made in May during the period between 1988 and 1996 in Ibaraki Prefecture.
The quantity of Japanese cedar pollen was measured at seven area points in Ibaraki Prefecture during the three-year period from 1994 to 1996, and was compared with the degree of Japan cedar wood occupation in each municipality.
Traffic volume according to municipalities in Ibaraki Prefecture was taken as a surrogate indicator of air pollution. The area otolaryngology facilities and doctors were taken as medical resources. Values were thus compared with allergic rhinitis morbidity.
Results Sixty to eighty percent of the allergic rhinitis patients examined in May were found to be suffering from pollinosis.
The quantities of Japanese cedar pollen scatter at the seven points in Ibaraki Prefecture varied in concert every year, the quantities correlating well with the area of Japanese cedar woods stands in each municipality in some but not in other years.
The morbidity in the records of allergic rhinitis according to municipalities correlated negatively with the proportion of the population occupied in farming (r=−0.38) and with the area of Japanese cedar woods in each municipality (r=−0.40).
The traffic volume calculated according to municipalities in Ibaraki Prefecture correlated significantly with the yearly average concentration of nitrogen dioxide (r=0.63, P<0.01) and with the morbidity of allergic rhinitis.
In places among the northern mountains of the Prefecture, both the morbidity in the records and the distribution of otolaryngology facilities were low.
Conclusions More than 60% of the morbidity from allergic rhinitis in May appeared in the National Health Insurance records to be associated with Japanese cedar pollinosis. This was confirmed by the correlation between yearly variation in morbidity and that of the quantity of Japanese cedar pollen scatter.
As local factors increasing the morbidity of allergic rhinitis in the records, air pollution, urbanization and a greater availability of medical resources were indicated.
