"In contrast with UC, there did not appear to be a significantly lower risk of CD according to latitude based only upon residence at birth or age 15."
The reason for this apparent association between latitude and inflammatory bowel disease incidence is not clear. However, "a leading explanation for this ‘north-south’ gradient in the risk of UC and CD may be differences in exposure to sunlight or UVB radiation, which is generally greater in southern latitudes. UV radiation is the greatest environmental determinant of plasma vitamin D and there is substantial experimental data supporting a role for vitamin D in the innate immunity and regulation of inflammatory response," the researchers noted.
Funding was provided by the National Institutes of Health and the Broad Medical Research Program of the Broad Foundation. One researcher reported previously being a consultant for Bayer Healthcare and Millennium Pharmaceuticals. No other disclosures were reported.