Regional variation in infant hypoallergenic formula prescriptions in Australia

There is little information on the regional distribution of food allergy in Australia. We examined the influence of latitude (a marker of sunlight/vitamin D status) on food allergy, as measured by 2007 infant hypoallergenic formula (IHF) prescription rates in children ages 0-2 yrs. Data were compiled from the 52 statistical divisions in mainland Australia plus the island of Tasmania (n = 53 observations). Data from the Australian Department of Health and Aging and the Australian Bureau of Statistics were analysed by statistical division. There was significant regional variability in hypoallergenic formula prescription rates (per 100,000 population/yr), with the highest rates in southern Australia (14,406) and the lowest in the north (721), compared with a national average of 4099. Geographical factors (decreasing latitude and increasing longitude) were associated with a higher rate of IHF prescriptions, such that rates were higher in southern vs. northern regions, and in eastern compared with western regions. Controlling for longitude, physician density and markers of socioeconomic status, southern latitudes were associated with higher hypoallergenic formulae prescription rates [beta, -147.98; 95% confidence interval (CI) = -281.83 to -14.14; p = 0.03]. Controlling for latitude, physician density and markers of socioeconomic status, eastern longitudes were also associated with higher hypoallergenic formulae prescription rates (beta, 89.69; 95% CI = 2.90-176.49; p = 0.04). Among young children, hypoallergenic formula prescription rates are more common in the southern and eastern regions of Australia. These data provide support for a possible role of sun exposure/vitamin D status (amongst other potential factors) in the pathogenesis of food allergy.