Distance from Equator ‘influences allergy risk’
MedWire News: Where children live - and specifically, the latitude - may influence their likelihood of developing skin and food allergies, research suggests.
The study authors admit that the reasons for this link are unclear, and propose a range of factors - from the temperature and sunlight exposure to infectious diseases and levels of vitamin D - to be tested in future studies.
Dr Nicholas Osborne (University of Exeter, Truro, UK) and colleagues studied around 8000 children aged 4-5 or 8-9 years who lived in regions across Australia.
For each child, Dr Osborne's team determined whether or not they suffered from allergic disease (eczema, asthma, or food allergy), as well as their latitude of residence (ie, how far they lived from the Equator).
Australia is a vast land mass, note the authors, spanning latitudes from 10°S to 43°S.
The researchers found that children who lived in the most southerly regions of the country - ie, furthest from the Equator - were up to three times as likely to have food allergies or eczema as children who lived in northern regions.
This was true for both younger and older children, note Dr Osborne and colleagues.
However, latitude did not appear to influence risk for asthma, they report.
"The results of this study agree with previous studies that have suggested a positive influence of increased ultraviolet exposure and vitamin D levels on symptoms of eczema and food allergies," the authors write.
They conclude: "Investigating these phenomena at a finer level by using meteorological data, such as temperature and solar irradiance, as well as [blood] measures of vitamin D, might provide more clues to the nature of these associations."
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By Joanna Lyford