Regional variation in epinephrine autoinjector prescriptions in Australia: More evidence for the vitamin D-anaphylaxis hypothesis

Background: There is little information on the regional distribution of anaphylaxis in Australia. Objective: To examine the influence of latitude (a marker of sunlight/vitamin D status) as a contributor to anaphylaxis in Australia, with a focus on children from birth to the age of 4 years. Methods: Epinephrine autoinjector (EpiPen) prescriptions (2006 -2007) in 59 statistical divisions and anaphylaxis hospital admission rates (2002-2007) in 10 regions were used as surrogate markers of anaphylaxis. Results: EpiPen prescription rates (per 100,000 population per year) were higher in children from birth to the age of 4 years (mean, 951) than in the overall population (mean, 324). In an unadjusted model of children from birth to the age of 4 years, decreasing absolute latitude was associated with a decrease in EpiPen prescription rates, such that rates were higher in southern compared with northern regions of Australia (β, -44.4; 95% confidence interval, -57.0 to -31.8; P < .001). Adjusting for age, sex, ethnicity, indexes of affluence, education, or access to medical care (general, specialist allergy, or pediatric) did not attenuate the finding (β, -51.9; 95% confidence interval, -71.0 to -32.9; P < .001). Although statistical power was limited, anaphylaxis admission rates (most prominent in children aged 0-4 years) showed a similar south-north gradient, such that admission rates were higher in southern compared with northern regions of Australia. Conclusions: EpiPen prescription rates and anaphylaxis admissions are more common in southern regions of Australia. These data provide additional support for a possible role of vitamin D in the pathogenesis of anaphylaxis.