Latitude Predicted EpiPen Use in 38 West Coast Cities
By Denise Napoli
Elsevier Global Medical News
WASHINGTON -- EpiPen prescriptions were more common in U.S. cities at higher latitudes and with lower UVB exposure than more southern cities, suggesting a possible link between vitamin D levels and allergic disorders.
For every increase in latitude degree, the number of prescriptions for the allergy rescue medication (per 1,000 people) increased by 0.6, according to the study findings presented in a poster at the annual meeting of the American Academy of Allergy, Asthma and Immunology.
"While we think that vitamin D is the most likely explanation, we also understand that these are population data, and that much more work needs to be done before we can say with confidence that low vitamin D causes food allergy," Dr. Carlos A. Camargo said in an interview.
Dr. Camargo, an emergency physician at Massachusetts General Hospital in Boston, and colleagues looked at the number of EpiPen prescriptions in 38 West Coast cities in 2004. Data were obtained from Wolters Kluwer Health, a Phoenix-based health care information services provider. The cities were in Washington, Oregon, and California.
The data were correlated with average UVB exposure and controlled for 17 demographic characteristics such as number of allergists, income and health insurance coverage status.
In total, there were 151,073 EpiPen prescriptions, accounting for 245,169 pens, or 7.45 EpiPens per 1,000 people.
People in Bellingham, Wash. (latitude 48.76), required the greatest number of EpiPen prescriptions at 15.77 per 1,000 people in the city.
The lowest number of prescriptions was registered in Bakersfield, Calif. (latitude 35.37), which, according to the Bakersfield Convention and Visitor's Bureau, records about 300 days of sunshine annually. Bakersfield receives approximately 50% more UVB over a calendar year than Bellingham. According to the researchers, there were just 2.11 prescriptions per 1,000 people in that city.
Although exact annual UVB exposure data per city weren't available, Dr. Camargo said that "the key concept is that, for the West Coast of the United States, latitude and UVB exposure are colinear (r = 0.93); a higher latitude equals lower UVB." And although Washington is a notoriously rainy state, "it's not the rainy days in Washington that matter, but rather the higher latitude, though rainy/cloudy days don't help."
In their earlier state-by-state analysis, Dr. Camargo and his colleagues also found that states in New England had the highest levels of EpiPen prescriptions, with 8-12 per 1,000 persons, whereas southern states--including California--had only 3 prescriptions per 1,000 persons (J. Clin. Allergy Immunol. 2007;120:131-6).
The strong north-south gradient in the prescription of EpiPens supports a potential link between vitamin D status and allergic disorders, the investigators concluded.
Dr. Camargo, a faculty member in medicine and epidemiology at Harvard Medical School, Boston, and his coauthors reported financial ties to several pharmaceutical companies on diverse topics. None of the investigators has financial ties to the food industry, supplement manufacturers, or the indoor tanning industry.