Background Although the most severe of the allergic disorders, the epidemiology of anaphylaxis remains poorly described. Hospital admissions for anaphylaxis in England more than doubled during the 1990s.
Objective To provide baseline data for assessing future trends, and to assess whether there is sufficient regional variation in incidence to allow efficient testing of aetiological hypotheses, we sought to identify any age, sex, geographical and socio-economic variations in hospital inpatient admissions for anaphylaxis.
Methods We studied all emergency admissions for anaphylaxis to English NHS hospitals between 1991 and 1995. Poisson regression modelling was used to calculate rates of anaphylaxis admission per 100 000 emergency admissions by age, sex, deprivation and by residence in urban/rural, North/South and East/West England.
Results Of the 13.5 million emergency inpatient admissions, 2323 patients had a primary diagnosis of anaphylaxis. Poisson regression analyses showed significant age, gender, geographical and socio-economic variations in emergency admissions for anaphylaxis: adjusted Female rate ratio 1.19 (95% CI 1.09–1.29), South rate ratio 1.35 (95% CI 1.25–1.47), Rural rate ratio 1.35 (95% CI 1.17, 1.59), and Non-deprived rate ratio 1.32 (95% CI 1.19, 1.46).
Conclusion This study identifies striking national age, sex, geographical and socio-economic variations in the incidence of inpatient admissions for anaphylaxis in England, affording important opportunities to generate and test aetiological hypotheses. Risk of anaphylaxis admission is considerably increased in females of child-bearing age and those residing in southern, rural, and affluent areas are independent risk factors for anaphylaxis admission.