A research group from the Tokyo Medical and Dental University Graduate School and the University Hospital's Center for Longevity and Healthy Life Promotion conducted a primary nationwide epidemiological survey of hypersensitivity pneumonitis and, for the first time in Japan, estimated the accurate prevalence and incidence rates (ed. note) of fibrotic and non-fibrotic hypersensitivity pneumonitis.
Hypersensitivity pneumonitis is an interstitial pneumonia caused by repeated inhalation of specific antigens. In Japan, there have been several epidemiological studies in the past that collected cases from specific facilities that specialize in diffuse lung diseases, but the prevalence and incidence rates are unknown, and no accurate epidemiological surveys have been conducted since then. Furthermore, there are only a few reports of childhood hypersensitivity pneumonitis worldwide, and no surveys have been conducted in Japan.
The research group conducted a questionnaire survey of a total of 2021 facilities targeting patients with a low diagnosis level or higher according to the guidelines for the treatment of hypersensitivity pneumonitis, based on a medical history between January 1 and December 1, 12. Responses were received from 31 facilities (1580%).
As a result, the prevalence of fibrotic hypersensitivity pneumonitis and nonfibrotic hypersensitivity pneumonitis (per 10 people) was 6.3 and 3.6, respectively, and the incidence rate (per 10 people) was 2.5 and 2.0, respectively, with fibrotic hypersensitivity pneumonitis being more difficult to diagnose than nonfibrotic hypersensitivity pneumonitis. Hypersensitivity pneumonitis was less prevalent in Hokkaido and the Hokuriku region, but more prevalent in the southwest.
Furthermore, because non-fibrotic hypersensitivity pneumonitis often has symptoms, we investigated the month of onset and found that it was most common in February and June, and rare in December. From responses from 2 medical facilities, we found that there were three cases of fibrotic hypersensitivity pneumonitis and five cases of non-fibrotic hypersensitivity pneumonitis currently receiving treatment, revealing the number of pediatric cases that are considered extremely rare.
As a result, it was found that the number of hypersensitivity pneumonitis patients in Japan is about the same as in Europe, and higher than in the U.S. Further epidemiological research is necessary, and the collection of case information in secondary surveys will enable the construction of the world's largest cohort, elucidation of disease characteristics, and revision of treatment guidelines.
Editor's note: Prevalence is the proportion of people per unit population who have a disease at a certain point in time (or up to a certain point in time). Incidence is the proportion of people per unit population who newly develop a disease within a certain period of time.
Paper information:【Allergology International】Estimated prevalence and incidence of hypersensitivity pneumonitis in Japan
