Ultraviolet B and incidence rates of leukemia worldwide.

BACKGROUND Recent research has suggested a relationship between vitamin D deficiency and risk of leukemia. PURPOSE Using data from the UN cancer database, GLOBOCAN, this study will determine whether a relationship exists for latitude and ultraviolet B (UVB) irradiance with incidence rates of leukemia in 175 countries. METHODS Multiple regression was used to analyze the independent association between UVB and age-adjusted incidence rates of leukemia in 139 countries in 2002. This study controlled for dietary data on intake of energy from animal sources and per capita healthcare expenditures. The analyses were performed in 2009. RESULTS People residing in the highest-latitude countries had the highest rates of leukemia in both men (R(2)=0.34, p<0.0001) and women (R(2)=0.24, p<0.0001). In men, UVB was independently inversely associated with leukemia incidence rates (p≤0.001), whereas animal energy consumption (p=0.02) and per capita healthcare expenditures (p≤0.0001) were independently positively associated (R(2) for model=0.61, p≤0.0001). In women, UVB adjusted for cloud cover was independently inversely associated with leukemia incidence rates (p≤0.01), whereas animal energy consumption (p≤0.05) and per capita healthcare expenditures (p=0.0002) were independently positively associated (R(2) for model=0.51, p<0.0001). CONCLUSIONS Countries with low UVB had higher age-adjusted incidence rates of leukemia. This suggests the possibility that low serum 25-hydroxyvitamin D status, because of lower levels of UVB, somehow might predict the development of leukemia.