Epidemiology of anaphylaxis in Olmsted county: A population-based study

Background: Awareness of the clinical features of anaphylaxis and its causative triggers is important if recurrent episodes are to be avoided. The incidence of anaphylaxis in the general population is often underreported, and epidemiologic studies are few. Because an accurate profile of anaphylaxis could heighten awareness of this problem, we investigated the epidemiology of anaphylaxis in the general population of Olmsted County, Minn. Objective: The purpose of this study was to describe the epidemiology of anaphylaxis in Olmsted County residents from 1983 through 1987. Methods: This was a retrospective population-based cohort study. The medical records of 1255 Olmsted County residents identified by computer-linked, medical diagnostic indices (the Rochester Epidemiology Study) were reviewed retrospectively to identify residents whose clinical episodes met the criteria for anaphylaxis. We determined the incidence and rate of occurrence of anaphylaxis, rate of recurrence, prevalence of atopy, cause of anaphylaxis, frequency of referral to an allergy specialist, hospital admission rate, and case-fatality rate. Results: There were 133 residents who experienced 154 ana- phylactic episodes during the 5-year period: 116 residents had 1 episode of anaphylaxis, 13 residents had 2 episodes, and 4 residents had 3 episodes. The anaphylaxis occurrence rate was 30 per 100,000 person-years (95% confidence interval, 25- 35). There were 110 residents who had a first lifetime episode of anaphylaxis (that was medically evaluated) during the years 1983 to 1987. The average annual incidence rate of anaphylaxis was 21 per 100,000 person-years (95% confidence interval, 17-25). Atopy was present in 53% of the cohort, and allergy consultation was obtained in 52%. A suspect allergen was identified in 68% of the cohort, most frequently a food, medication, or insect sting. The hospitalization rate was 7%, and 1 patient died. Conclusion: The incidence of anaphylaxis is less than 1%, and death rarely occurs. People with atopy experience anaphylaxis more frequently than people without atopy. Anaphylaxis frequently is not recognized by patients and physicians.