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 (beta, -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 (beta, -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.